Just want to give my two cents on this matter.
I personally love the new engineer class. I'm sure others out there do as well.
I think the main reason as to why most folks don't particularly enjoy it is because they want it to be something that it isn't. From what I've seen is the devs are trying to maintain a classic party structure since the patch. Engineer is everything the devs said it would be. I'm sure they'll be doing some changes to it, they always do.
As far as pros and cons, the only thing I see that seems to not live up to the hype is one skill and one ruby. The skill being Steel mosquitos. Decent damage, but if the mobs takes one step, or gets knocked down, it cancels it. Seems only useful if you're nose to nose with your opponent. The ruby is the self destruct one. It doesn't do nearly enough damage to be considered a self destruct. Barely nicks the opponents HP. Here's what I think they can do to make these better.
Steel Mosquitos: Since it works as a debuff on the enemy, make it to where it can only be canceled by purification, antidote and similar effects. Have it stay in effect until it wears off.
Self Destruct: Increase the overall dmg. Also make it to where when you rank it up, it will also destruct any devices you have on the field causing additional damage. May want to add some sort of cooldown to this so it isn't abused and no one complains. lol.