Why I think "tank" builds are so strong

Personally, I think the main part of the issue is akin to the issue with on-hit builds. The items by themselves don't seem too strong, but when you build them together it just stacks up making the moderate damage turn into insane damage. And it's in more ways than one. Now, one thing that can be seen is that the tank builds work best with champions with AA-enhancers or AA-resets, or ones that can synergize with Grasp of the Undying. Both of those work really well with since the AA-enhancer/reset will proc the spellblade, and it adds to the damage when Grasp goes off. In addition, Grasp of the Undying synergize incredibly with due to added healing and constant consideration of "in combat". Now remember, by themselves, the items are relatively mediocre. But when you take 4 mediocre things and put them on top of eachother, it can become a bit hard to handle. And there are some other items such as that give some good tank stats and add damage for being tanky, specifically on auto attacks which if everything adds up for each proc to happen on one single auto attack, it will seem to do an insane amount of damage, when in reality it is just 5 or so different sources of "meh" damage. Honestly, not sure how to fix this.