Here are my thoughts, but I wouldn’t recommend taking them as a final word…
(3) 5* Malicna–I wouldn’t recommend grinding any of these for training, if that’s what you’re asking. At the very least, I’d put them through the Hero Academy for a trade.
However–In the 2021 sneak peek, we were told there would be a new way to make our heroes progress. We were also told when the Hero Academy was released that SG still wants to make a new use for duplicate heroes. There might be a way–emphasis on might --to merge Malicna duplicates in the future to make her stronger. I’d recommend hanging on to them at least until we see this new system. Once you give away a Malicna, there’s no getting it back.
(2) 4* Griffin–I really like this guy. I would very happily keep two of him for wars and challenge events.
(2) 4* Rigard–Could be useful for wars, especially if you draw his costume. If you already have a long list of higher-priority darks, you might not get around to maxing #2, though. Depends on how long your dark list is.
(2) 4* Chao–I don’t think you’ll need Chao if you have Griffin. It might be worth keeping one, but not two.
Edit: Further thoughts on Chao–Since I don’t have nearly a full 5* roster, one Chao is nice to have for this specific scenario–Suppose you’re at war, and you’re trying to finish off a strong player. There are 3 heroes left, Alfrike’s the one flank still standing, and you’re trying to ghost tiles down the middle. Alfrike’s charged up faster than you would like. Chao makes a good safety measure to cut that mana down & buy some time so you can finish the job before disaster strikes.
(2) 4* Sabina–I’d only keep one of these.
(2) 4* Li Xiu–Personally, I don’t have much confidence in Li Xiu. I don’t know what your yellow roster looks like, but it might not be worth keeping either of these.
(2) 4* Scarlett–It may be worth keeping both of these, even if it’s only for burning through 4* challenge events. Her tile damage is impressively high.Can you make a good anti-titan squad with 4 reds in it? If you don’t have enough reds to do that well, then that would be another reason to keep Scarlett #2.
(2) 4* Melendor–I think you’ll only need one, but I’d also sit back to see what others have to say
(2) 3* Gramps–I’m that one guy in beta who says Gramps isn’t even worth having. In a Very Fast tourney, I’d still rather use C. Isshtak, C. Berden, Shrubbear, or… Well, pretty much anything. If Gramps were a healer too then it would be a different story, but he doesn’t do that. I say his mana boost is insubstantial, his resurrection chance is too low, and even if he brought someone back near the end, it likely wouldn’t be a game changer.
Also are these 3* characters worth keeping and leveling:
Vollermork–I despise Vollermork. I often heckle minions in general, and this guy’s no better. He is tanky, though. It’s possible my views are warped, but if he were average speed for the same effect, he still wouldn’t seem the shiniest to me.
Morris–This guy’s fun. I hear he’s not that great, but eh, I don’t know enough to say that.
Gramps–As I said before, I don’t have confidence in this one. Unless someone else sheds some miraculous insight that completely changes my perspective, I’d chuck them both.
Helo–In my book, he’s one of the best 3* healers in the game. I’d happily keep him.
Chick Jr.–??? I have this one, and I don’t even know what to do with him yet. I haven’t even tried yet to find whether he’s worth it.
Berden–I like his costume, but if you don’t have it, I consider him a stormtrooper for heavy green stacks in tourneys & things. I’d recommend keeping him, unless you’re already happy with the 3* green stacks you can make without him.
Costume Friar Tuck–I don’t know about this one…
Costume Jahangir–I still haven’t found a substantial difference between this and the basic one. But I think he’d be worth using in Very Fast tourneys.
Kailani–Nope, wouldn’t keep this one. Gunnar’s better with his brick wall stats, though.