I think that we need more itemization changes more than anything.
Like an item that gives you Movement Speed when you are hit by basic ranged attacks (melee only) or one that slows enemy ms when they hit you with basic attacks (like old Randuin).
Some changes to armor and magic penetration items, as they are too good (LW and Void Staff I mean). I would love to see those items to be good against tanks, yes - but I would also want them to be rather ineffective against squishies. I think about something like this:
Last Whisper
+40 Attack Damage
+0,15% armor penetration per point of armor enemy champion have capping at 45% (300 armor)
So it wouldn't give you that 18% additional physical damage against squishies (80 armor, most champion get that much at level 18) - it would give you 5% instead. However, against that tanky 300 armor Rammus (well, 300 armor isn't THAT high for rammus) it would give you 51% physical damage increased as opposed to 36% from the current one.
Really, right now LW and VS are pretty much the best choices for the last or next-to-last slot regardless if enemy builds Armor/MR or not.
If you have 260 AD (I assumed 100 base + 160 from runes, masteries and items combined) then buying LW is worth about 95¹ AD against that 80 armor target. This is quite high (3420 gold worth of AD) considering that it's also the worst case scenario in late game. Against that 300 armor Rammus it gives 145¹ AD (which is over 5k gold worth of AD). It scales with your AD (the higher it is the bigger the benefit). It's very similar with magic resist.
¹ - may vary from champion to champion, based on their abilities. Took only basic attacks into account.
I think those 2 items should be changed into anti-tank exclusives, so if you want to deal with that tank you will sacrifice some of the damage against squishies.
