OP's experience is pretty much identical to my own. Every point he had is 100% accurate and was my experience as well when running AS1. My group (AST/SCH) ended up making it past Faust but wiped to the Oppressor @ 50% on our best attempt. I have never felt, with any job other than AST, that I was pushing a class to its utmost potential and still have it fall short. It was obvious that I was having mana issues despite managing it very well, it was also obvious that the entire group was being forced to overcompensate for my lack of DPS because throwing out a single combust would result in a dead tank. At times, Benefic II spam wasnt enough, even with LS and a mind potion.

I am determined to make this class work but for the time being, I have been replaced by a WHM. I don't think this is the experience that SE intended.