I have used mouseover macros for all my previous healers [shaman being my favorite and most used healer].
Mistweaver mouseover spells don't seem to be working the way they do with other healers.
While channeling Soothing Mist on mouseover'd Target A [while having a mob or boss 'physically' targeted], the insta-cast Enveloping Mist and Surging Mist do not go to the mouseover'd Target B.
Maybe I'll have to click targets to heal 'em after years of mouseovers. :(
...orrrrr this is how Mistweaver has to work.. re-mouseover new target, re-cast Soothing Mists to get insta-cast Surge/Envelop. Almost like casting Riptide/Renew followed immediately by Greater Healing Wave/Greater Heal etc, just Soothing Mist acting as the initial HoT.
tl;dr -- might have answered myself with my own post.