Rogues and hunters mostly. Engineering for paladins is for like 28 and less level paladins. But paladins should never wear cloth and engineering goggles are all cloth. Engineering is good for hunters but before they should go to the thunder bluff weapon master to train for them.
You can make plate helms as Engineer
http://thottbot.com/i32473
http://thottbot.com/i32472
http://thottbot.com/i32461
and bombs helps a lot in pvp, arena or instances; better than been Blacksmith.