In terms of live-streaming, viewership is usually higher at the beginning of raid and savage/ultimate trial cycles, especially during the race for world first, or when the devs add new, bigger content, like PotD or Eureka (this may or may-not include copycat content like HoH or next phases, like Eureka has). Plus, PvP seeming to only be somewhat big in EU.
Right now, content creators who just live-streams don't really have that much to stream (I've seen a few branch out into other games). :/