It seems like heavily defensive AP champions are getting a bit too close to being OP strong

I am starting to notice that and now even are becoming massive raid boss like beasts that can soak up shit tons of damage (which is precisely what they should be doing, so good job there RIOT), but are able to deal a disproportional amount of damage as well (that is not so good). Whether they build 100% full tank, or work some AP in there, they end up getting to a point where they basically need 3-4 players focusing them just to whittle them down. All of them even have some kind of shielding, damage reduction and/or healing worked into their kits. But the main issue here is that each of them have % Target's Maximum Heath damage, high base damage stats on their abilities, and multiple sources of CC, often times hard CC. The CC is the least troublesome as it defines their role. But the "free AOE damage" is what is the true issue.

"Free AOE damage" + damage reduction, shielding, and/or healing is what could lead them to becoming broken. You cant have massive % TMH as an AOE on top of high base stats and increased survivability in most cases. I am seeing ADCs, who should eventually out scale tanks and win out in the late game vs them, not even scratching them and taking so much return damage themselves.

I am not saying there is too much of an issue quite yet, but they are getting close to being a major concern.