I am going 2H DPS Engineer, as well, though, I am taking a different route. My focus areas are passives and the gun bot, as when it comes out with the higher tiers, it will increase all of your damage for the entire duration that it is on the field.
Once I hit level 35 with my Engineer, my playstyle definitely became more lively (I purchased the charging ability that rushes you forward at your target and releases bolts, upon collision with the enemy, that give you back 5% of your mana for each enemy hit). Throw a concussion grenade, followed by some spider mines, charge in, and finish with the lightning cleave ability. Rinse and repeat until all enemies are neutralized.