I mean it's obviously extremely difficult for anyone to get much reliable comprehensive information concerning the situation, but from how it seems to me after reading articles from different sides & discussions with some refugees, is that for the Syrian population Assad is just as much a threat as ISIS. This perception actually differs greatly from how things are portrayed in western media, understandably, where ISIS is sometimes even mentioned as the only perpetrator.
It's understandable of course, seeing as ISIS is openly and very agressively hostile towards the west, while Assad's motivations seem to be primarily power-driven, but it paints a very distorted picture.