I must be doing soemthign wrong, tank vs damage.

So, to be clear, this is an issue ive been having for quite some time in game, and typically assumed that i had to be doing somethign wrong, playing a champ wrong, wrong build order, take your pick.

But after a game today ive decided to jsut publically address the issue and see what ive been doing wrong this whole time.

Basically, my issue is tanking vs going damage, on jsut about any champ. but lets use poppy as my main example since i was in a poppy mirror match when i finally snapped and went off about it.

Basically, it was poppy vs poppy toplane, and ive been struggling to make poppy work for me since her rework. I was a full tank poppy, she was a tanky juggernaut poppy, she had more AD, but i had far more armour, without giving up that much AD. At one point in the game i checked our stats and i had 85 armour, which was -30- more then she had, and she had 120ish AD, which was -40- more then i had at that time.

She moves in to do a trade, i have a minion wave and shes tnaking it, so i figure its a good trade to make, she goes in, i block her stun with my W, we trade Q's... half my HP gone form one full Q, meanwhile she takes a full Q from me and she barely takes 15% of her HP in damage. So what did i do wrong there? how do i take SO MUCH MORE DAMAGE when i have so much more tank? how does she get by while taking almost no damage at all? why does building damage jsut beat buildign tank?

Move to later in the game, lee comes up for a gank, i assume im straight up screwwed becuase im low, too low to go 2v1 so i run to my tower, lee marks me and i panic flash, my W isnt off CD yet, enemy poppy is rushing at me. in a panic i mash buttons and intrupt lee's dive with my E, im still low, too low to survive it poppy connects with even one ability. somehow i survive when my W comes off CD, poppy still has over half her HP and lunges at me, i W, then book it, the tower kilsl her on the spot. somehow maigcally i survive a 2 man dive while tkaing literally no damage and having less then 10% of my HP left.

I recall, get back to lane, and poppy is all over me AGAIN, she ignores my minions, and jsut goes all in, and nukes me with NO EFFORT. and by this point that doubel kills has given me my deadmans plate so i have a TON of HP and armour, soemthing like 150 or so by now and shes only got one damage item. so why does a champ who just died during a 2 man tower dive, giving her opponent 2 kills with close to even CS, jsut nuke someone who went pure tank? what am i missing here? and to be clear my runes and masteries are tnak based too, with small damage boots from assassin, and my keystone. My runes are my "taric" build runes which are some scaling HP runes, scaling MR runes, and ALL THE ARMOUR runes, becuase most toplanes are AD. i start the game with an absurd amoutn of armour, and still take a crazy high amoutn of damage.

Now lets flip to when i buidl damage vs tank. when i go ADC, or even toplane fighter champs, i build damage, duh. and when i see a tank i groan becuase for some reason even when i build a lord domi regards, i jsut dont ever do damage to them. so why when i buidl tank do i never sotp damage, and why when i build damage do i never do any? Ive looked at guides, ive made itemization calls based on champions in the game, i buy MR vs AP, and armour vs AD... what am i actually doing wrong here?