Moonvine is basically a heavier version of Amaryllis, who's quite decent for single target attacks. It's just a shame that raidbosses are designed to NOT kill them ASAP, but rather to let them live as long as possible to let everybody take a stab.
It would be nice if raidbosses worked a bit more like SEGs in PeroPero: way more health, with stacking bonus rewards for finder, highest damage and killing blow, but smaller rewards for everybody else hitting it. Then Moonvine (and single-target units in general) would become way more interresting in my opinion.