Okay, well to be honest you have more heroes and farther along than I was guessing based on your asking if you should consider some 3*'s. Based on this new information and how long you’ve been playing I’m going to now assume you know some basic things like, ‘if you want to improve your Titan scores, Wu Kong will really help there.’ I’m also going to assume that if your roster has a substantial gap you will notice and fix it (for example, raids made it obvious I was short on debuffers, so the moment I pulled Sonya and Caedmon they became top priorities).
So I’ll just address the point I was making about Trials. I’ve re-sorted your heroes by their class, and will differentiate between anyone who is field-ready (let’s say 5* 2.60, 4* 3.60 or better), and everyone else.
Assets: Grimm, Little John, Gormek, Namahage
Assets: Elkanen, Rigard, Agwe, Mnesseus
Assets: Gobbler, Caedmon, Melendor, Melia
Fighter: Magni, Boldtusk, Colen
Assets: Hu Tao, Sumitomo, Rudolph, Valen
Monk: Leonidas, Wilbur
Assets: Joon, Wu Kong, Li Xiu, Valeria
Assets: Justice, Cyprian, Sonya
Ranger: Evelyn, Triton, Buddy, Chao
Assets: Khagan, Evelyn
Rogue: Jackal, Scarlett
Assets: Danzaburro, Kelile
Sorcerer: Sabina, Skittleskull
Assets: Ameonna, Gill-Ra, Chochin
Assets: Merlin, Kashhrek
Now combining them to trials (only listing field-ready heroes)
Strength (Barbarian and Fighter)
Kagburado, Magni, Boldtusk, Colen
Fortitude (Cleric, Druid)
Mysticism (Sorcerer, Wizard)
Sabina, Skittleskull, Proteus
Serenity (Paladin, Ranger)
Arthur, Evelyn, Triton, Buddy, Chao
Survival (Barbarian, Rogue)
Kageburado, Jackal, Scarlett
Justice (Monk, Paladin)
Leonidas, Wilbur, Arthur
Decimation (Fighter, Wizard)
Magni, Boldtusk, Colen, Proteus
Nature (Druid, Ranger)
Evelyn, Triton, Buddy, Chao
Shadows (Rogue, Sorcerer)
Jackal, Scarlett, Sabina, Skittleskull
Piety (Cleric, Monk)
I think the cases I’d focus on are where you have three. If it’s below that - Fortitude - it’s too much to push for right now. Plus, if you address your strongest weak cases first, that will probably improve the other areas. Your weak weak cases will probably become strong weak cases by the time you’re ready to re-evaluate. And where you have four or five serviceable heroes I’m going to assume you’re fine (manage with healing, items, etc.), which takes care of Strength, Serenity, Decimation, Nature, and Shadows.
For Mysticism almost all of your options are purple. Merlin is my pick. As a bonus, he also brings your Decimation roster up to five (which is basically why I’d focus on the cases with three heroes) while giving you a boost in raids, titans, war, and events.
For Survival Grimm seems pretty clear and also provides a nice pair with Arthur (in non Trial situations). Again, that pushes another trial up to a full five, this time Strength.
For Justice I’d choose Wu Kong, for the aforementioned titan reason. And, let’s face it - if you’re shorthanded you are hoping to take advantage of variance and get lucky. Wu Kong facilitates that. He’d also be the third in Piety, so you’ll be in a better position to address that in the future.
If you’re doing color matching training then your red and green resources are not yet claimed. There’s no obvious red target to my eyes. I would consider Namahage, but since you’re already fine in the trials where he’d play I think I’d ultimately pass. Kelile catches my eye, as you are thin in both of the trials involving her class (Rogue). I don’t think that’s an amazing usage of resources, so do what you think is best and be ready to switch if you pull someone who feels more valuable.
Green is interesting. A Druid seems the natural choice since you have none, and both Caedmon and Melendor are viable. I’d probably decide based on whether or not you need another healer.
As a side note, I don’t think taking ~3 weeks would be a waste on Mnesseus, though I’d like it a lot more if he were a critical fourth or fifth piece than the first. But let’s say you do Wu Kong, giving you a third Monk. You still have no clerics to add to that for Piety. Now Mnesseus has some value. Ultimately I’d like Rigard here, but I think it’s stronger to let Merlin claim the purple resources.
All that said, this is all assuming you are interested in the trials! Good luck.