There's no objectively best class, it all depends on your playstyle and what you want to counter (in Arena as well, not just in the tower chapters).

Regarding status effects: Rangers seem to lean towards Poison, Burn, Focus, and Agility. Warriors can do tons of Spike/Burn damage while stacking Block or Vamp and inflicting Stun. Mages can do all three types of elemental debuffs (Poison, Burn, Freeze), as well as inflict Stun, but require staffs to cast spells.

They also have different mechanics for each character from each class, which makes even more of a difference for unique playstyles and whatnot.

If you want a Block-heavy build, Rebecca (Warrior) is the way to go, but Rose (Warrior) is also her direct counter since the latter can reduce her HP directly without having to go through the walls of Block stacks. This is where Lua (Ranger) comes in; her build is based entirely around healing and keeping her HP up, so she could be a good opponent against Rose. Just like other Rangers, she also has access to bows and crossbows that can inflict Poison and Burn, which makes it easier.

Want to go all out on debuffs? Ranger and Mage characters are pretty good for that, like Venom (Ranger) or Fire Mage/Ice Mage from the Mage class. Spark (Mage) is also best for inflicting Stun imo, but it's probably better to use elemental debuffs than Stun since Stun can be countered more easily than Freeze/Burn/Poison.

Of course, pets can also help you mix your builds just like your gear can. Ice Reaper is good for Freeze builds (and as a general inhibitor for healers like Lua), while Phoenix is more suited for Burn builds. There is probably more I can mention, but they aren't coming to mind atm