Hmmm Engineer OP... I mean every character is OP if you spam abilities.
Without the stun, Engineer is pretty vulnerable. I do agree that Double Time is too strong. I also think the turret has too much HP at the moment. Overall, the Engineer should receive slight adjustments to speed and perhaps turret HP. But anything more, would be too severe for this character.
Oh yea, unlimited ammo whilst standing next to the turret is ridiculous. I thought this was absolutely BS since the release of the game. I think the increased fire rate is alright, but unlimited ammo is too much..