Overall, I really love the class design in this game! But I have a few nitpicks I feel compelled to voice for future fine-tuning.
Tech Hunter - Skill 2 (Grenade): The mechanics of the skill interact well with the rest of his kit, but the skill overall feels very sluggish to use. I'd love to see the projectile speed INCREASED, and the cook time DECREASED (so it explodes faster). This would preserve the functionality of the skill overall but make it quicker to use altogether, allowing for more seamless combos and less interruption to shotgun DPS.
Pandora - Passive (Haunting Luminary): This is a very underwhelming passive; I feel like it should simply be a base function of her first skill. Then, she could receive a new, more flavorful/interesting passive.
Pandora - Skill 2, final evolution upgrade (+1 use charge): Again, this is a really underwhelming final evolution. Most final evo upgrades for skills are interesting and unique; this is not. It's basically just a stack of an in-game item, which feels generic and doesn't interact with her kit in an interesting way. I think replacing this evo with some sort of elemental damage boost would be much more flavorful for her lightning motif AND synergize with the elemental damage of her Skill 4 evolution upgrades.
Echo - all targeted skills (but especially Skill 1): Echo's targeting function is neat, but it doesn't translate well to gamepad, because there's functionally an aiming "dead spot" between your character and the reticle. It would really help controller play if, in the event there is no enemy within range of the reticle, his skills activated on the closest enemy between the reticle and Echo himself. This would retain the targeting function, but still allow gamepad players to hit enemies that wander close to them, outside of reticle range.