Well, I did not expect it to take a whole month for me to do some more playing with this, but I did get back to my previous character, played around with it a bit more, and can say that, having worked in Dwarf, and SOs, it's bloomed very quickly. Here this character is in the mid-20s where a Kheldian would normally be be trying to find a way to slot everything and make Dwarf useful, and I'm hot-swapping forms multiple times throughout fights, taking full advantage of each one as needed. This is, legit, how Kheldians should feel and I'm having a pretty great time with it.
The update to Gravitic Emanation helped, and Gravity Well doesn't feel too bad, for me, just because I have access to the ranged attacks in Dwarf form (in fact, my usual fighting habits involve shifting to Dwarf form once I get some aggro, then briefly back down to Human anyway when Gravity Well finishes recharging, because that Hold is just too useful). Mire, in practice, didn't turn out to be too bad, either.
My general mission picks haven't had me dealing with too much mez-related frustration so far, so I can't comment there; I certainly wouldn't mind some SoA level protection in the passive (it'd help at low levels, especially), but so far, Dwarf is sufficient for me.