I rarely post suggestions so boy am I afraid to state this, but I have some stuff to say about Arena.
I love it, it's a really fun PVP mode that isn't unfair or daunting to take part in so I feel comfy just hoping into rounds and playing around with synergies and team makeups.
However the main downside to it is the fact that the bots are broken as heck to play against if you don't have a team that can DPS enough or tank enough to knock ‘em out, I already know that this is likely so you can’t just rack up arena wins quickly and get the shop rewards without any real challenge but incidentally it makes losing repeatedly in a bot-heavy lobby {which most are rn} incredibly demotivating since by that point you're already so far down on hearts that catching up would have too come out of a raw fluke!
Now to fix this, the obvious route would probably be to idk lower their AI so they aren't as difficult to deal with. But that takes the fun out of it, that takes thee fun out of triumph over the machine. Instead I think it'd be much better to promote the Arena a lot more and give more context to it rather than just “PvP” as that's a phrase that will often scare people off. I know myself if a game has PvP in it I steer clear of that since it's usually aimed in favour of folk who've either been playing long enough to be top of the chain or have the meta in a chokehold.
Arena, doesn't work like that at all, it works more like Super Auto Pets. And the fun of pvp in that game is the fact that we all start equal or equalish, someone you fight and win one tourney may absolutely shove you into the dirt the next, it's less about having broken characters and more about workshopping the best scrappy team you can on the fly.
I think if people knew thats what Arena here is like, then they'd be a lot more inclined to give it a shot, which would also solve the issue of bots being prevalent as heck and the demoralising situation that is knowing that the rewards are likely gonna go straight to some bot programmed to know the game iinside and out. It's way more fun seeing it go to someone who's been thrown into the deep end just like you!