Seeing how engineer turrets are weak and underpowered, I think a good start to buff them would be to have their skills activated constantly instead of you activating it. No one is going to avoid using them when they’re out anyway, and turrets are just plain weak when their skills are on CD or not used.
Not to mention a single AoE in higher level content wipes them out completely. It’s a joke.
Cooldowns on the turrets are too long as well.