Vivica - I never use her, not even in war, really. Though I have her costume maxed also, so she’s pretty decent, I just have better options. Sadly, I don’t really have any better 5-star Yellow that would’ve be better off getting emblems though, the only Yellow I have waiting at 3-70 is Norns, and I don’t really plan to ascend her/them.
Grazul - I tried using her for a while during Telluria’s heydey, but even then, she wasn’t all that great. She now only gets rare usage in wars under very specific circumstances. Right now, I’m waiting on two potential ascensions in Red, I have to choose between Marjana and a second Tyr… so if I could have the Grazul mats back for either of them, I’d take it. (I will probably ascend Marjana - I love Tyr #1, but I think the variety will be better than the duplicate for now.)
Honorable (or dishonorable?) mention goes to Kunchen… but not really. I mean, I wish I could get the mats back from him now because I never use him anymore, but he was one of my early powerful 5-star healers, and he helped me stay in high Platinum and low Diamond, so I suppose I don’t regret him. It may seem odd, but I prefer my Costume+19 Rigard, of which I have two… I use them before I use Kunchen.
I’m also going to state my disagreement with some others here - at least for me, Clarissa is a hero that I use daily, in many, many raids. She and Gravemaker go together very well, and just pile on damage, and then my other three heroes get picked based on the tank color, typically. Sure, Clarissa doesn’t hit as hard as Gravemaker, but she’s not too far behind, and she’s got durability and speed!