Thinking of Skarner, Sejuani, Shen, Dr. Mundo.
Even tho items like Heartsteel fit those champions' kits really well with their HP scalings, I can't really see the idea behind the buy. Knowing how jungle is a snowballing role and that the first items are of a bigger importance, I find it hard to pinpoint the advantage that Heartsteel gives over other cheaper options.
Is the idea just to arrive to a gank or short fight with the massive +900HP ? To proc your bonk and leave ? Or is it the freedom jungle gives to your build ?(not needing more AoE with pet, "getting away" with buying item pair synergies like Unending Despair and Spirit Visage) (by getting away, I mean that you don't get punished by a greedy buy as much as if you were playing a lane). Or, if is it as simple as that tanks don't have that many good options (because it feels like it sometimes)
For most, if not all other tank items, I can easily categorize them and choose the one I think its the best for every situation, but I'd love to see how other people think of and categorize tank items