Wow. Your leveling is all over the place. Time to settle down and pick one hero in every color to max. Doing same-color training and focusing on one rainbow team at a time is the way to go. Let me preface the advice I am about to give by saying that you can use whoever you want for world levels and such while you follow my leveling advice - if you choose to follow it - because some of your heroes right now are clearly stronger than the ones I’m going to advise you to level. But if you keep leveling like you are going, you are going to eventually have some gaping holes in your lineup.
Since you don’t appear to have a maxed 3-star rainbow team, I’m going to stand by my original suggestions about who to max first. You’ve already done Bane, so finish Balthazar, Valen, Hawkmoon, and whatever you think is your best 3-star green. You can get these folks up to snuff relatively quickly, and you will have a team that should be able to progress pretty far in the world map, finish the rare tier of challenge events, and be somewhat competitive in most raid tournaments limited to 3-stars. Also, you get 6 flags in alliance wars, and it takes a LONG time to build a bench of 30 good heroes. These folks will serve as a late war team for you for a long time to come. I still use every one of these heroes in every single war my alliance is in. It is important to score loot in as many different ways as possible; this is why you should get this base team under your belt.
Now, I rather like having at least two of every color in 3-stars. Again, you can use them for later war teams. Also, each month’s challenge event includes enemies that reflect one of the colors (i.e. can’t be damaged at all by heroes of that color, and instead, turns the damage back on the attacker). Really annoying. So, with 2 in every color, you can switch out the hero of the reflected color with a hero that is strong against the reflected color (e.g. a second green hero for events where the reflected color is blue). Pretty nifty. Finally, you need to build a broad roster in terms of classes. You can complete the first two stages of most trials using teams made up mostly or entirely of maxed 3-stars. I just got my first 4-star cleric up to snuff last week, for example. So consider hero classes when choosing who to level as well. Those emblems may not seem like much now - I still have a pile of wizard emblems I haven’t given to anybody yet - but when you get a hero to give them to, you’ll be glad you’ve been collecting them. Since you didn’t list the rest of your 3-stars, I can’t really tell you who to go to if you want to go 2 deep in 3-stars, but I suggest you strongly consider doing so.
The other nice thing about doing it this way is that you can continue to round out your roster of 4-stars (and collect the materials to level them) while working on a good 3-star base. So, while you have two great heroes in Boldtusk and Kiril (I’m jealous, btw; I don’t have either of them yet) I don’t think they work that well together. Both give an attack buff, but they differ in duration and intensity, and one overwrites the other, so you aren’t getting the most out of either of them by playing them together. You have two really good options in red besides Boldtusk - Gormek (who has the defense down that nobody else on your team has) and Scarlett (who hits like a truck). So maybe you prioritize Kiril for your first 4-star team (better than Boril, since you have Cyprian already) and leave Boldtusk till later while doing one of your other good reds. But most people I know would take Boldtusk and Grimm over Kiril and Gormek/Scarlett any day. You don’t have Grimm now, but you might by the time you build a double rainbow 3-star team. See where I’m going?
It’s a marathon, not a sprint. It’s annoying to work on lesser heroes when you have some big hitters on your bench, but ultimately, it’s worth it. I just drew Gill Ra today, and I’m seriously considering maxing her after I finish Rigard, and before I go back to leveling Domitia. She’s the only 3-star cleanser, so there is a place for her on my roster, even though my main team has a team power over 3600. There is A LOT of stuff to do in this game. Depth is your friend.