I'm no game dev but If pick my favorite DPS, Healer and Tank based purely on fun.

3. Machinist - Because I am biased and I am a sucker for anything Mecha. The animations are cool (love the flips). Going wild with OGCDs during burst windows makes my dopamine receptors light up with glee. Not too much downtime. Fluid to play thanks to freedom of movement.

2. Sage - The most fun healer to play. I like being able to drop a party wide shield and 10% damage reduction buff before AoE damage hits. Having on-demand heals on the move. Being able to dot mobs or spam AoEs during wall to wall pulls while simultaneously sustaining the tank thanks to Kardia. Satisfying OGCDs. It's has more than 1 DPS button which helps break up the monotony. You have to keep an eye on your shields so you can make the most of your Adersing charges. It's easy to pick up, but there's a fair bit to master here which I like. I wouldn't have minded a few more DPS buttons to make up a mini rotation. If it worked a bit like Disc priest in wow where optimizing your damage output also causes you to output more heals that would have been perfect. There's room for improvement, but it's still fun to play. My favorite healer easily.

1. Gunbreaker - A jack of all trades tank with tools to fit any situation. DPS wise, I enjoy playing this over any other DPS. There's virtually zero down time in the rotation. You press 123 twice and you're already back to bursting. The cooldowns line up just right with mini bursts followed by big bursts followed by mini bursts. Super satisfying. Defensively, you've got just enough self sustain with Brutal Shell, Aurora, and Heart of Corundum. Raid wide defensives that you can pop before big damage hits and feel like you are helping.
There's meme potential with Superbolide Macros >

I really can't find much to complain about. GNB is why i continue to play this game. It's fun, it's got a cool theme. And I definitely do not simp for the quest giver NPC.