Jouk, Nordri, and Helo are the top 3 rare heroes I see.
Do you need EDD? It’s hard to pass up Nordri otherwise. If you need a healer, Helo. But I leveled Jouk for the same reason you mentioned. Dispel is fairly rare for three stars. I don’t have a list, but it’s possible he’s the only dispel all.
If you want to prioritize titans and events: Nordri
Otherwise Jouk
cGunner is defense down who is blue. Nordri is elemental defense down in blue. The two together will stack. Great for titans, event teams, tournaments, etc.
I would do all 3 Nordri, Helo and Joukahainen before doing any other blue heroes. They give you a solid base of heroes to play 3 star things and it doesn´t take an eternity. You can go back to 4 and 5 stars after that.
It just depends what part of the game you are talking about. For events you have to have Nordri, there is no way around him. Also out of the 3 he´s best in bloody battle and he´s most important if you want to build a strong 3-stack. In VF you have Helo against treevil and Jouka against Faiez. Also Jouka is best for buff booster tourneys. There is no 1 hero who does everything. Which one to start with is mostly dependant on what else you already have, if you have other healers Helo is least important, if you don´t he´s most important. The other 2 can work by themselves, Nordri does more damage, Jouka is a specialist against buffs, which is more of a niche, but he´s good at what he does…
I would hold out for Azmia over Boril. Boril tends to be useful early on but to fall by the wayside fairly quickly
Helo is good for 3* tourneys except Bloody, and is a fast project. Jott as others have said is good versus Titans (requires some timing and practice of course)
I like Jarvur and the rest of your fast blues too. Speed is so important. I’d level them all in time Immunity to new status effects can be handy as well (Gato). I like my Boril very much as well