Or do a bit of both. By no means am I saying that this IS the solution league is looking for, but I believe that this will help the game greatly.
***Buff ALL champions armor by 5, MR by 2 increase scaling of all champions armor by 1, HP by 50, and MR by 1.***
No compensation nerfs (yet) no compensation damage buffs.
What I believe will happen.
Trades, all ins, burst, poke and damage over all will take longer reducing the effects of damage over all.
I personally think that damage is not too high, rather defense is too low. Right now there are certain champions like Sion, Garen, or Mundo that - despite the amount of damage- have tools that allow them to still be very effective against it. Therefore give a small amount of tools to everyone and those extra damage effects like electrocute and DH now become less effective.
Sustain Damaging champions will become much stronger.
If this was to go through, burst damage or ones-shotting would be highly mitigated, making champions that need 100 damage after blowing their whole kit and cant do it less valuable than a champion that can more so.
Tactical approaches to a situation will become more prevalent.
When making tactical plays you get more time to think, outplay, dodge, wait for a cool-down. Even if that is seconds League is a game of seconds. This should have a positive effect on the overall strategy of a game as well. Rotations, objective, control etc. as kills are not as easy to obtain.
Mistakes are not as easy to punish.
While this is certainly a doubled edge sword, with the new bounty system I believe this is better for the game as someone with a huge bounty can't make a huge mistake like 5v1ing as it will still more than likely be claimed. However, making a small mistake like trying to ward the river with no back up and (the 0/5 Jax +3/6 Lee Sin getting the drop on you) isn't as easy for them to punish and lose 15 minutes of hard work to get that bounty. You may still lose your flash, but securing your bounty is more important. The other side of this is that bigger mistakes that should be punished are not. To that All I can say is there would probably be more situations that the person should have survived than he shouldn't have. (From a neutral perspective) It's too much of a "What if" situation.
I say "I believe" or something to that effect a lot because I am unable to analyze data to see how effective this would be it's all speculation, but since this is preseason this is definitely something we can try right now. It helps with 2 big complaints. Damage Creep/Damage Too High and Defense is Too low.
Buffs/nerfs can happen after the dust has settled on this change.
There are definitely cons with this solution, but I believe the Pros outweigh them.