I think what puzzles me most about the Cinder change is an issue of consistency
Riot made it pretty clear that they want Tank items to be chosen based on the unique aspects they bring to play, not simply which one has the best raw stats.
And then Cinderhulk gets its passive weakened, and given more raw stats to compensate.
Have you guys considered making a new non-smite item with the +25% bonus HP passive and then buffing Cinder's burn aura tremendously to give it that potent early-mid game niche you're interested in?
EDIT: just to make things clear, the %HP passive on said new item would share a named passive with Cinder (or Cinder would just drop that passive in favor of a much better burn aura, I don't know which would work better.)