The vault mission is simple, once one knows what to do and with whom. If one's team is OK, it can be done with one player doing the objectives while another serves as a wingman, and the rest on guard duty.
I have already a few missions under the belt, and failed only a few at the start. In the end, it is easier then the elite STFs.
But again, there is a huge problem with this mission, or even two. For starters the bloody schedule means one can only do it every other day, perhaps even once per week, especially for European players such as myself.
I've done it a few times since last Friday only because I can only play STO while at work. But finding competent people to play with, it gets really frustrating fast. If you don't have the freedom at your workplace as I do, then you're screwed.
The other problem is it is just another nearly endless grind to get the purple MKII sets, something in the order of almost 130/140 missions. That won't fly with me, I won't do this mission 140 times, absolutely no way, especially with the scheduling issues.