Okay so Rook.
Rook is kind of like Taya in that he needs teammates that know how to set him up, and he has trouble against ranged DPS. If a teammate can make someone burn their escapes before Rook dives on them, he can wreck them. He's got good burst and sustain DPS, even without Berserk.
His problem, of course, is that he's slow and has one bad movement skill. His charge has startup time and is low-priority. So he needs that setup. I don't think, like I've heard some people say, that he needs to proc berserk on the counter to be good. If he can get those procs, he's fine. But I've had decent success with him taking the snare on Berserk usage and just using it as an AoE snare.
Against ranged teams, he'll probably want to take the charge battlerite, rock-does-armor-break-and-extra-damage battlerite, and then the reduced rock cooldown one. In a ranged duel when playing footsies, he can rack up a pretty high protection score by staying in front of his teammate and being a meatshield, using rock on anyone who tries to use anything with a cast time (or to zone people into setups for his teammate), and using his counter and EX M1 to keep his health up.
I've had a lot of success playing him alongside Poloma and Varesh. Rook can protect Poloma fairly well by using rock to peel for her, and otherside can get him out of some tight spots. Alongside Varesh, he can still peel with rock, and shield helps him in tight spots. Additionally, the combined extra-damage-taken debuffs can result in someone getting burned down really fasy if they get caught without escapes. And the two of them do pretty well at zoning enemies out of the center and forcing them to come in or give up the orbs. I did have some games where we just sat in the center and picked up orbs until sudden death forced opponents in, then we smashed them.
People really don't want to get close to Rook, which means you can bully people around just by walking toward them, and sometimes tossing rocks. I find it's often effective to do this if my teammate is advantaged against whoever he's fighting - like a Croak chasing a support, and then when the support runs out of escapes and Croak wants to disengage anyway because he can't get in again, I dive in. Same on ranged DPS. Then the other person tries to jump on me and the Croak gets to stealth in again.
But I've also had some games where either the teamwork wasn't there or the opponents were just playing it careful. He's got no escapes, so Rook is actually fairly vulnerable to being dived on if his teammate can't help. That's happened to me a few times.
My current feeling is that at the level I play (around 2700), Rook is pretty good. If it turns out he's too weak, or too swingy, I'd probably look at improving his rush. If in practice it's actually just that easy to keep him out, giving his rush higher priority (keeps Bakko from interrupting it with his charge) or super armor (doesn't get knocked back or interrupted by non-melee knockbacks/interrupts) or a projectile reflecting shield (if it turns out that the Bakko matchup is mostly fine but he's basically dead against ranged) would probably help. Making his Berserk immune to Clarity would help the Poloma matchup. Giving his charge iframes on the startup and maybe early part of the rush would make him much less vulnerable to AoEs. Making his charge immaterial on the early part would help making it less easy to trap him by body-blocking.
Right now the biggest problem I have with him is that you literally can't get out of some AoEs, because space has a long startup time and you have no iframes. So if an astro wants to stone you, he can. Or any other similar targeted circle of death type thing.
If it turns out that doing that would make him too good in the matchups he's already too good, probably a solution would be to reduce his damage a little bit?
Anyway, tl;dr for this is that Rook's power level is hard to evaluate because he has some really easy matchups and some really hard ones, and his performance depends on a lot his teammates not expecting him to play like Bakko or Shifu and engage and disengage constantly.