i think heavies are in an even worse place right now than lights, because they cost so much more. light tank at least has niche uses, even though mediums are typically the real option. you can at least make the bare minimum cost light tank, slap that in your production line, run it in garrisons, and feel okay about it. and you can squeeze a little more sf support damage out of them. neither of those are much, but they're *something*.
i can't come up with any use case for heavy tanks where i couldn't just use mediums. in sp, you can get sufficient armor with mediums (which frankly you don't need anyway, but if you want it you can get it for cheaper using mediums). in mp, fixed superstructure mediums (for td) will dab on armor gouged heavy tanks too easily, at a comical fraction of the cost of getting enough armor where that's even necessary. thus i can't picture when you'd design and build these.