White's changes are fantastic, and in my opinion make for an objectively better flowing map. Love the additions. Glacier has had that little dead end room walled off, and an ammo crate has shifted from the lower indoor area to closer to the ramp.
Hazards are currently on a two-per-week cycle by the looks of things. Last week was Dagger (love that map) and Reactor. This week is Ghost and Giant. If you haven't played them yet, Ghost has on-and-off acid rain cycles that, if you're caught in, will eat away at your shields. Super tough. Giant is supposed to be night, illuminated by more frequent cannon fire, but it's still too light to be of any significant change. Looks pretty, but that's about it.
BioWare did say they were just testing out this method of hazard maps releases and if it doesn't work try something else. I think it would be better to just have them in bulk with a little option to tick if you want the hazard variation of a map. Same for unknown: tick a box if you want hazards to be included in the pool.