We simply don't know how many missions Vincent has completed or missed before, because it was never mentioned.
I don't see Vincent failed protecting Lucrecia and Hojo, because those two fxxxed themselves up
. Like, they wanted to do some voodoo to themselves. You can't really interfere with that
If we say Vincent wasn't able yo save Lucrecia, then yeah...he didn't try to stop Gast, L and Hojo early enough. He doubted their choice and accepted it for a while and only took action later.
But I'm not sure Vincent allowed himself to be shot...I mean yes, he was careless/bad enough that Hojo shot him, but he didn't intentionally want to be shot...
I like the idea that Vincent has a reputation being an excellent Turk, but a legend...iuno. Does his reputation among the Turks surpass that of Sephiroth among SOLDIERs?
I also don't understand why would like, the top killer/spy/agent/whatever be sent to be a bodyguard. Isn't that a waste???
I always have the theory that Vincent wanted out or he wanted to find his father or some shit. But thats completely my imagination