Could be. I would switch Hawkmoon with Sonya, because I don’t like healers on the wing. Less chances of actually being beneficial to your team. Sonya is fast so she could definitely be able to use her special attack on the wing.
Wilbur is said to be a game changer on basically every aspect of the game. His attack boost and shared damage will be a huge advantage to you concerning survivability and damage output. I would basically include him on everything with the hero bench you have now.
Proteus could be considered as a game changer as well. Mana block has shown to be useful for all aspects of the game as well. Titans and event/quest bosses not firing their special attacks. Your raid attacks being easier, because you can prevent nasty special attacks from firing. On raid defense, he could possibly do the same if the AI fires it correctly. But seeing he aims at 3 targets, the AI will have a better chance at using him with more benefit for your team. Basically, a great hero considered his mana block. He also has a DOT effect, so that makes him even more useful.
That depends on what you’re facing. If you fight a green titan for example, including both Hawkmoon and Wilbur will increase your score quite a bit already. I never use a rainbow team unless I am farming. If you want to read about the benefits of color-stacking, here’s a thread about that: Titan Attack Fundamentals - (new player Titan guide)
You can still use Hawkmoon for a while, especially when paired with Wilbur. His shared damage will make her survive longer in battles with higher difficulty. I would however level up Belith and replace her for Brienne as the healer for your team. Her special attack is more valuable than Hawkmoon’s. Nevertheless, Gadeirus heals himself and nearby allies. Paired with Wilbur and next to Wilbur, his healing ability could be sufficient enough for some parts of the game, but a ‘‘heal all heroes’’ hero is of course a better option.
Danzaburo is a gambling hero, but the 2 ‘‘useful’’ parts of his special attack are in fact very useful. As he is your only 4* yellow, I would definitely consider leveling him up.
I don’t have a lot to say about Gadeirus. Perhaps someone can tell you more about him.
Not yet, I would suggest you to focus on your 4* heroes first. They are easier to level up and have less ascension material costs, but will give you the possibility to get every ascension material from quests and events.
This means I would continue working on:
Wilbur, Proteus, Danzanburo, Sonya, Gadeirus (or Belith first)
Once you can’t ascend them any higher due to a lack of ascension materials, you could work on your 3* heroes in order to give your hero bench more depth. Also, instead of blue and red 3* heroes, Kelile and Boril are good options to bring to 3/60 also.
Melia, Namahage, Gato, Gil-Ra and Belith are the 3* heroes I would work on first.