Spend some more time on the demo and here are some small revisions based on some testing.

offensive
Vanguard:
high risk as always, but also highest HP and offensive king skills; melee does a lot of damage, fastest melee, and only class with running melee.
Adept:
Second fastest melee, about the same speed as sentinel, biggest range on melee but it recovers a tiny bit slower than the sentinel; other skills provide lots of battle control.

well rounded
Sentinel:
Tech armour makes this class a walking tank, but lacks any super offensive skills, good/fast/cool melee with good range too.