Missing a single positional isn't a huge deal on monk, and it's pretty much always better to hit a GCD than to delay it to get a positional off. The thing with Monk is that our two non-positional skills, Touch of Death and Fracture, were removed for SB. So *everything* that's no an AoE is a positional now, and if for some reason you can't do them (like certain stack mechanics, or bosses spinning like douchebags, or standing inside walls, etc.) then it can be mildly vexing. Not a huge problem by any means, though.
On the fights where positionals don't matter, like Royal Menagerie phase 3, I find myself still moving side to side simply because *oh my god* are melee boring without positionals.