I run Engineer presently for unlocking my SMG's...I can tell you, the RPG's are definitely not op'd. If anything they're underpowered. From full health, with no engineer repairing it, it often takes a minimum of five RPG's to take a tank out. If you're constantly being ganked by RPG's you're positioning yourself poorly and not retreating back when you should be. You're likely sustaining damage from mines and other stuff before being taken out by the RPG's as well If you're being hit on the sides, top, or back you'll also take a bit more damage.