I've noticed the level 50 mobs east of CoL have three different groupings that inhabit that whole eastern area. I didn't think much of it at first, as maybe I'd just run into a slightly different spot, but when I was working on dailies for Icewatch rep, I was actually able to get another set of quests thanks to the mobs switching.
That said, I'm wondering if this is tied to an RL timer or conditions within the zone. Of the groupings, one in includes Redsnow human types as well as yeti, the second being Stormwatch humans and air elementals, and the third being werewolves with bats. The dailies mainly differ, though there are a couple that overlap. As is, this bumped a 6k rep gain to 9k, and if the third can be done in the same day, it'd make 12k possible if I'm recalling all the possible quests properly.