Solution to Tank Assassin/ADC/etc. Builds: Bonus Health Changes
Currently, there are some Assassins and a few ADCs who would rather build Tank than build damage. While a bruiser build shoukd certaintly be a little viable, Tank build just shouldn't be a thing. This why I suggest: Changing Bonus Health from Flat Bonus to Percent Bonus Based on Base Health Similar to health and mana regeneration, changing Bonus Health this way can make it to where building tons of health is more of a Tank thing and other classes would rather build Armor and Magic Resist, which can be built around much more easily with armor and magic penetration, which is more common in items than anti-health.
It would be like this:
+10% Health
+25% Health
+15% Health
+12% Health
+50% Health
+20% Health
+35% Health
+35% Health
+35% Health
+40% Health
This way, somone with 500 + 80 per level base health is getting much less benefit than a Tank with 600 + 95 per level base health. A typical build with health items with a Warmog's will have about +155-190% increased base health. This will make Tanks with 2135 base health get more out of health items than an Assassin with 1835 base health. More importantly, however: This allows Riot to balance Tank builds by adjusting the Assassin's or non-Tank's base health and not their abilities, giving them more options for balance than giving them huge ratios and tiny base numbers "But isn't this a buff for Tanks?!" No, not until super late game at least. At Level 1, Tanks have about 580-680 base health. This means that Ruby Crystal will give them 58-68 base health as opposed to the current 150. This also means that Tanks that perform well early and are near unkillable are no longer so since they no longer have insane defenses early on. Maokai Top Lane is no longer a huge brick wall early game.

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. So I believe that tanks will have lots of base health and will have their items tuned to reward building lots of base defenses over health items.
. These are common items in the builds of a number of mages & supports. This would be even more punishing to medium to short range mages who have to get closer to the battle to dish out damage.