Slipknot was a nobody included to enforce the idea behind the suicde squad, except it was so obvious he was gonna die and be the only one dying that the movie gave way to what the recent version of the comicebook bigest flaw. The suicide issuppose to be a team where anyone can die, but that stop being the case since the new52 revival. Anyway comparing a ugly middle aged man with hardly any screen time doesnt really compare.
Katana is basically the mulan of the DCU consistent Asian representation. Despite never really having big following she never really dissappered from the eye of DC The fact that she almost got her live action theatrical debut before wonder woman says alot. She pretty much made an appearance in every DC animated ensemble piece i can think of. Katanna doing just fine
Cassandra is basically a silent Hitgirl but less violent
she will be well received as along as they dont screw up her introduction. Yes she will get a boost, it would not surprise me if BOP is revived and she is on its future lineup. There is only up from here after her live action appearance.