Pretty sure Teeming mobs can't get Infested as i've seen from Nnogga's mapping so far.Also BfA skittish is exactly the same as Legion skittish. The general threat nerf to tanks has not changed a thing about the threat generation tanks have during skittish.
The problem with so many levels of difficulty is that it furthers power creep throughout the expansion.They really should consolidate normal and heroic dungeon difficulties into one segment. Normal dungeons always become irrelevant later on in the expansion anyway with other forms of content offering higher ilvl rewards. I also think they need to do the same with the raid difficulties, LFR and normal should be merged, call it normal and let people queue for it like they do in LFR now or let guilds zone in and clear it.
Grievous looks horrible for healers, gonna be rough weeks when it's up.