Whats Wrong Combo

that stroker should be pushing that converter a lot higher, i would guess upwards of 4000 rpms.... that cam cant pull at lower rpms, that duration cam should make power from somewhere around 3800 up to 7000 or so.... I would look into a tight converter or maybe the cam timing is off a little.
short shifting may help some, also try launching at a slightly high ide, and flashing the converter in stead of power braking it. if that doesnt help its tme to look into why the converter is so tight ,or why the motor is so low on torque. ... just my thoughts on this , i am sure you will get a few different opinions .

a couple more thoughts, how is your 60 ft time ? wheel spin ? your 60 ft should be 1.60 , or better to be hooking up . if you are spinning a lot the down track times and mph will suffer also. make sure you have the right chip in the two step, if you are launching off of it. trans brake ? with out one that converter may not see 3500 rpms on the foot brake ( over come the brakes and spin the tires )