Definitely max at least one Kiril. The defense boost has helped my heroes survive attacks that would otherwise kill them.
Dupes of BT, Kiril and Rigard are great for war depth.
You have one Melendor maxed; why not one Sabina too? She’s like a purple Melendor, and would be great for instances when Melendor isn’t suitable (say, against Red buffers like Ares or opponent BT).
Vivica is an amazing healer, and more importantly one of the few Yellow healers, and I think the only Yellow cleanser. There will be instances when she’s better to bring along than Delilah. Definitely worth maxing IMO, wish I had her.
Aeron can be useful, but I see why you might not like him if you already have Kunchen or Rigard or Grazul, who also cleanse. I only have Aeron among the 3 though, and there were times when it was more useful to prevent a status effect (like Azlar’s DOT or Kunchen’s defense debuff), than to wait until the next turn to cleanse it. But I agree that Aeron could be lower priority.