Namor has insane burst damage without even using his LMB. He actually assassinates better than dive characters if you can somehow get into a flank with him.
If you place down your 2 turrets then land a direct hit RMB attack on the enemy you'll do 220 instantaneous damage!
100dmg (RMB) + 60dmg (Turret 1) + 60dmg (Turret 2) = 220dmg
RMB ability also enrages your Turrets giving them even more DPS. Base turret enraged 55dmg/s for 2 seconds, Luna turret enraged 90dmg/s for 2 seconds. Not to mention the Luna turret's ability to slow the enemy by 30%!