I guess you could all it an exploit or just working the system. But Vex + a Dragon Mote with stacks on it is beyond utterly amazing.

I've gotten Vex returning 800-900 hp/s on reasonably stacked motes and up to 2-4k hp/s on highly stacked motes. I laughed when I found a 99 stack mote once and ascended into Godhood. This of course can lead to an Inquisitor easily soloing nearby elites (that might take at least a little work otherwise) or in a couple cases entire parties on pvp servers.

Might be something to consider.