Id run Witter at PG, Collison at SG/SF to offset the defensive liability.
I think some of the mixed results may be due to the IQ differences (Witter with B vs. Collison with A-). I personally like high speed/high ball handling in flex at my guard spot.
I think you are also losing because you have bad shooters set at +1/+2 Per frequency. Fike and Witter should be set at 0/ -1. Looks like their set at +1/+2 right now. Let Witter utilize his BH and Speed to score, dont make him shoot threes (id suggest -1/-2 for him).
Lowering your Per frequency, will make those guys attack the rim.... Both Witter and Collison are great free throw shooters, let them get to the line... i mean for godsakes Collison is shooting 96% FT.