Managed to test all the characters in beta and here is my take:

Best starting hero to solo all the story missions:
Ajax (Tanker with good DPS)

Best starting hero to transition into void realm boss fight:
Viessa (ice cc skills can slow down the boss so teammates can focus fire on weak points easier)

Most OP end game hero:
Gley (High hp, high def, high dps, unlimited ammo). Pair it with a skill extension and -30 defense down pistol and have Sharen as a teammate to reduce enemies defense and you can pretty much melt everything. Cons: Boring skills.

2nd best end game hero:
Sharen. Good fun skills. Equip the battlesuit melting nuts module to debuff bosses or any enemy defense (-50% if I'm not wrong) with her 3rd skill and use beam rifle with battlesuit crusher module to minus enemy defense by 50%.

Best support and laid-back playing:
Jayber. Set up your turrets and watch as all enemies die without you doing anything. Best if you have the attack turret module that makes you able to spawn 2x attack turret. All enemies will die as soon as they spawn (tested at the last map defense mission)

Edit: Thank you for all the awards and thumbs up. Really appreciate it.

I would like to add on that most characters are fun to play but some character are much better in end game boss fight where it really matters. For example, Bunny is extremely fun to play and you just erase enemies by just running around. However, she is a not the best to have in your party for very tough boss fights. But hey play what is fun for you. I'm the type that rather play the meta. All these test were done in Beta so you can take it with grain of salt as I do not know if there was any buff or nerf done to the characters but the logic is there. All the best Descendants!

2nd Edit: Hi guys, thanks for all the positive feedbacks and so many of the awards especially "take my points" awards. Wow. Truly appreciated! Now I can by more themes :)
Yes this review was from Beta as clearly stated. After 60 hours of playing the actual game, I would like to update that indeed Gley is still OP! Check it out on youtube immortal Gley or Infinite ammo Gley. Actually, alot of characters are good for bosses too like Freyna, Viessa, Enzo etc.

All characters should have no issue with the bosses as long as you invest in def and hp mods. So I recommend that you play what you like. It's gonna be a long grind with all these crystals that you have to get to polarize all your slot modules if you really want to make your character op in hard mode. Otherwise it doesn't really matter. I have a buddy who finished the story without using his 500k kuiper credits because he didn't know what to invest on. He got a good scolding from me alright 😂 So moral of the story have fun and if you want the most accurate current tier list, I suggest you check the list from youtuber named Moxsy. That's the best one I've seen. And yes Bunny is the best for farming. I use Gley as my main and Bunny for farming. Take care and have a good one! 😊