I 100% recommend Blast Fencer and especially Galactic Knight. You're basically a Jedi, lol. The melee combos you can do once you get to Galactic Knight do insaneeee damage. I'm sad to have switched off it honestly.
What's the focus on the class and how is the TP gain on that class?
I've just been sticking with Full Metal Jaguar because I rack up TP like no tomorrow and overdrive combos do a ridiculous amount of damage and benefits.
Doing combos from behind the enemy + buffs mean I rarely ever have to wait for cool downs and I don't have to waste TP on unnecessary moves, just buffs.
I tried the sniper class and it took a while for it to get going and do decent damage. It's a lot of work and I guess it's alright. Just focuses more on arts since TP gain is slower on that one.
And the Psycorruptor class is basically a heal/support while the team does stuff. I think QisTopTier uses that class.