Been running this build since I picked up my XL300. I find I do better (dmg wise) with the pulses, and I don't particularly like missles in this game in general ( the dmg tends to hit multiple segments every shot, due to spread/tracking ) I've shaved down the cockpit and front side torsos cause of the smaller hit boxes, that I never seem to get busted. Leave just enough to survive a lucky ( unlucky ) strike. Had a scare or 2, but have yet to lose an arm or the mech to a head / front side hit. Heat seems to be fine, if you work in and out and give it a chance to cool. Definately need to be pro-active on hot maps thou ( I tend to go for chain as opposed to split sets ).
Well, I think you should leave this build for the relatively crappy JR7-K. The advantage of the D is the 2 missile hardpoints.