I've been a bit out of the loop with WoW for the past 2 months, so I didn't even know we had any information at all on the new seasonal affix. But as it turns out, the only information we do have is its name: Domination.
So, I'm curious to hear what people think this affix will bring with it.
My personal theory (keeping with the theme of Anduin becoming corrupted in 9.1) is that it would mind control (i.e. "dominate") a random player periodically and the others would have to do something to free them. This could be something as simple as damaging them down to 70%, or something more involved such as rescuing their soul from nearby and bringing it back to the mind-controlled player in order to free them.