BST doesn't get invites mostly because people regard it as a "solo job."
People view WAR and MNK as a low man job, they still manage to get into larger groups though. It isn't really what people think of the job as much as "is the job the best ever? Yes/No?" If you are best, congratulations people will invite you.

Regarding the ability though... was it said that this summoned the pet when used? Else it seems like a good ability to use towards the end of a jugs life. Oh, I've used 25 of my 30 mins of pet life, time to use 5 mins of super power to get the most out of it.