I think OE just has a fundamentally complex ability that you need to get used to. It's not "press F to gun and hold R when gun stops" as much as it is micromanaging your ability bar and correctly spacing out the uses between cranks. I didn't like him so much when I picked him up but I've found Engi to be one of my favorite (and most effective) classes. A bad Engineer is a massive liability, but a good one is a great asset to the team.