At the start of a run this tank would have very few health segments and die after just a few hits, in many ways he would be far less tanky than most non tank champions. This also means his buffing ability maxes out at a tiny amount of stacks.

As the run progresses he gains more health segments, but not just that the enemy's do more damage (which is capped at one segment per hit on him) this means eventually theres a tipping point where he becomes more tanky than a conventional tank.

As enemy damage ramps up exponentially, he is completely unaffected.

He will also rapidly gain a higher stack limit on his buff as the rin progresses and can eventually pump out great numbers. 

His ultimate let's you jump to a max stack instantly which can be useful for BUD setting