A first class average of 38, mostly playing in the second division, does not suggest that Moeen is quite top class - it certainly does not compare at all favourably with the numbers Bairstow, Ballance, Taylor etc have acheived, more often in division 1. When I've seen him bat, I've found him easy to watch but have always thought his game a little bit lightweight.
So I suppose the question is how much of a difference does his off spin make? Hard to tell the quality at this stage, because whilst he has picked up some good hauls these have been on very helpful wickets in division 2. Whilst Swann is playing, I'd say little - either of the B's has the attacking game England seem to require from their number six and Joe Root is perfectly efficient at getting through a few fill in overs. There may be more of a vacancy if and when Swann calls it a day and England are forced to look at whether they really have a Test class replacement available to them.
Incidentally, the stuff about Worcester respecting his faith made me cringe; pure proselytising.