All you have to do is pick full Marksman team for the enemy , why ?
1- THORNMAIL 
2-They are paper !
2-You can tank them so hard 
What to pick as marksman ?
Don't pick 
etc they can be ap or burst tank
NO MATTER HOW MUCH HARD THEY PENETRATE ALWAYS WINS .
Btw full support team is bad idea , why ? 1-High CC 2-So much heals
If you lost a game vs the marksman team PLEASE TELL ME !
Ariaflux1 votesAgree with list except replace Ashe with Draven.
Deep Terror Nami1 votesI saw one person mention their strat was give the enemy all tanks, and the team just builds % damage 
AtheosisX1 votesAs long as you don't give them tanks that can effectively build damage it works pretty well.
1011001110001 votesWhat happens when the marksman decide to build any combination of the following items:
And now aren't totally paper and can sustain past the Thornmail damage? >_>
Evil Jester2 votesWhat happens when the marksman decide to build any combination of the following items:
And now aren't totally paper and can sustain past the Thornmail damage? >_>
Morellonamican, plus if you rush thornmail first they wont be able to farm enough to buy that build till its way to late.
1011001110001 votesWhat kind of team could you possibly get where you build both 
AND on ANYONE?
Also, if you rush , and they already picked up 
, 
, and/or some random damage item, what are you gonna do, peek-a-boo the adc to death? If you rush , the default go to just becomes the lifesteal items that are literally about 1000 gold more expensive or less - , , , or even if they managed to get that far ahead in cs.
Evil Jester1 votesWhat kind of team could you possibly get where you build both
Also, if you rush
Since a large number of tanky champs scale off of AP, morellos would be benificial. but you wouldn't even need it as thornmail counters life-steal, not the other way around.
Thornmails damage is calculated BEFORE Armor, while lifesteal on the other hand is calculated AFTER armor. Meaning that the more armor the tank builds, the less life-steal will absorb meaning more damage will be dealt than healed always.
Thornmails damage will remain constant, while lifesteal will not.
The only thing the ADC's can do to prevent this is to build MR as thornmail returns damage as magic damage, but if ADC's were to build MR over damage, there damage output would be greatly reduced making it worse, even building maw, or banshes would be pointless as thornmail does not trigger there on hits.
1011001110001 votesSince a large number of tanky champs scale off of AP, morellos would be benificial. but you wouldn't even need it as thornmail counters life-steal, not the other way around.
Thornmails damage is calculated BEFORE Armor, while lifesteal on the other hand is calculated AFTER armor. Meaning that the more armor the tank builds, the less life-steal will absorb meaning more damage will be dealt than healed always.
Thornmails damage will remain constant, while lifesteal will not.
The only thing the ADC's can do to prevent this is to build MR as thornmail returns damage as magic damage, but if ADC's were to build MR over damage, there damage output would be greatly reduced making it worse, even building maw, or banshes would be pointless as thornmail does not trigger there on hits.
You're assuming that you guys will be out of laning phase and already in the middle of massive teamfights for this then, because most adcs alone can finish 
before even taking out the enemy tower, so marksmen can rush instead, trade with you, and utilize the lifesteal on minions. That's not a difficult concept to grasp.
And you're already under the presumption that giving them ranged champions means they'll just build adc items. If you gave me any of the champions you listed, I'd probably build the aforementioned and , mitigating your Thornmail damage, increasing Lifesteal effectiveness, making me tankier, forcing about 1/3 of all armor you built to become useless, granting tenacity, and now I have 2 slows.
Thornmail is not going to just hand you games, ESPECIALLY when you list off , , and as potential marksmen to give them. The first is basically an adc-caster, the second one busts tanks with infinite-stacking rend and kiting, and the third one's entire laning phase revolves around burst combos for trading and all-ins.
And this is all assuming they don't decide to just give you squishies like 
and 
instead.
Evil Jester1 votesYou're assuming that you guys will be out of laning phase and already in the middle of massive teamfights for this then, because most adcs alone can finish
And you're already under the presumption that giving them ranged champions means they'll just build adc items. If you gave me any of the champions you listed, I'd probably build the aforementioned
Thornmail is not going to just hand you games, ESPECIALLY when you list off
And this is all assuming they don't decide to just give you squishies like
Thornmail alone wont win the game, but you cannot out-heal thornmails damage, you can out damage and kill the tank, but you can't out heal it. Its mathematically impossible because it deals damage first and foremost, armor reduces AD damage, witch reduces healing from lifesteal, building those MR items reduces your damage even further meaning you will heal even less. Even if you build those MR items is just means they have too build more armor and you will still take more damage than they receive.
Even with spirit visage, it will only increase your life steal stat by 6% as it only increases healing effects, bringing you to 36% with that build which seems like alot till you realize the dps you sacrificed with those MR items.
If you have >233.3 effective armor, Thornmail will reflect more damage than you receive, assuming the attacker has 0 magic resist; if they have 30 magic resist, >333.3 armor is required. Other words, as long as they continue to stack armor, thornmail will deal more damage than the tank receives. as far as Autos go. now since thornmail only reflects autos, then yes it is very much possible to kill a tank by basing and bursting abilities through kitting, but with tanks like 
who ult to reduce damage even further and can gapclose or push off an ADC. ot
who can also close in you you with a flag dash or ult it would be very difficult to kit them. Not that anyone in Nemesis would pick these champs for you but I speak hypothetically of course. but if you insist of playing using you abilitys more than autos then your better off building straight damage for the burst than you would be with MR.
would not help you as you IF are versing an armor stacking champ, which would reduce the Current HP% passive damage and because the heal from the active effect will not be equal to 10% of the target's health because it is calculated after considering damage mitigation effects such as ARMOR.
would reduce the tanks armor to deal more damage, but with those MR items you built, you reduced your DPS making this item less effective long term.
Conclusion, thornmail alone as you said will not win the match for you, but you cannot out-heal it's damage or mitigate it.
1011001110001 votesThornmail alone wont win the game, but you cannot out-heal thornmails damage, you can out damage and kill the tank, but you can't out heal it. Its mathematically impossible because it deals damage first and foremost, armor reduces AD damage, witch reduces healing from lifesteal, building those MR items reduces your damage even further meaning you will heal even less. Even if you build those MR items is just means they have too build more armor and you will still take more damage than they receive.
I don't need to "outheal", I just need to kill the tank before he kills me. I don't even need to build THAT much damage if you're really going for the amount of tank you want, meaning I can "sacrifice" dps for tankiness and other forms of survivability.
Even with spirit visage, it will only increase your life steal stat by 6% as it only increases healing effects, bringing you to 36% with that build which seems like alot till you realize the dps you sacrificed with those MR items.
It won't matter as long as I have more damage and better sustain than you. Outside of a full-fledged fight, I have a better chance of surviving simply because I have an effective means of regenerating hp by auto-attacking minions or jungle monsters.
If you have >233.3 effective armor, Thornmail will reflect more damage than you receive, assuming the attacker has 0 magic resist; if they have 30 magic resist, >333.3 armor is required. Other words, as long as they continue to stack armor, thornmail will deal more damage than the tank receives. as far as Autos go. now since thornmail only reflects autos, then yes it is very much possible to kill a tank by basing and bursting abilities through kitting, but with tanks like
Yeah, congratulations, I built Spirit Visage, now I have 85 magic resist. Now how much Armor do you require to make Thornmail more effective? 450? 500? A virtually unreachable number? If you seriously continue to stack armor so much just to make Thornmail an effective item, then you're sacrificing your own damage potential. And I can build Last Whisper and effectively negate 1/3 of your progress with an item that is just as expensive as Thornmail. Meaning you would need to build an unrealistically high amount of Armor to actually bring Thornmail to that state of effectiveness, a pointless effort and moot point.
also has its own lifesteal, attack speed, and its Active has Soft CC in the form of a slow. I'm not building it just for shits and gigs, but I assume as a tank you will be building items with health stats that will continuously increase the effectiveness of , and coupled with , it will become a significant item, despite you having a lot of armor (which is going to amount to 2/3 of their values specifically because of )
I put -1- MR item in that build. I don't even NEED that much damage output if I'm just going to be fighting a team of tanks that you're presuming to get to fight against these marksmen, I just need to outdamage them, which is pretty easy with the build I highlighted.
Conclusion, thornmail alone as you said will not win the match for you, but you cannot out-heal it's damage or mitigate it.
Except I gave the perfect example of an item that directly mitigates its damage, another item that cuts your armor stats by a third, and lifesteal items which, at your calculated 36%, are all I really need to sustain through a teamfight.
