The biggest issue with SF is that he is S. L. O. W.
JTR teams will take a billion turns before he gets his taunt off, and the AI (in my experience) is smart enough not to attack SF until he has taunt up. The other issue is that a single taunt is really easy to dispel, and SF has no way to cleanse buff-immunity off himself, so he quickly becomes dead weight.
If you pair him with a fast Thrawn that could do a TM-swap and get him taunting, that may help, but I don't have any experience trying this.
SF is a pretty good toon with a nice kit, he just doesn't quite stand up to the META. He has a really nice usefulness for defensive teams in TW though, as he IS a plug-and-play tank.
Hope this helps