Currently, we can kill garuda HM in 3:30, taking away another 20 seconds for que time/loading and cutscenes thats 156 myth an hour.

If they don't make new content drop more than 40 myth somewhere, or make it drop gear that's decent, then garuda HM will still be the fastest way to farm myth. And with each new piece of gear garuda HM dies faster. I reckon will be under 3 mins within the next week or two. And thats 1 tank, 1 healer, and 6 dps.