An ME priest can ALWAYS support. You aren't as effective at support as a full support priest but you can offer blessing, agi up, and heals just as good as any FS and for 1 point you can offer magnificat. Level 1 magnificat is just as good as level 5 you just need to cast it more often and because you have more dex as an ME priest you cast it faster than that dope with all the vit. You also get Lex Aeterna along the way getting ME so it's good to party with an ME priest for hunters and wizards. You may also get pneuma as an acolyte (strongly suggested) making you great in a party killing penomenas, firelock soldiers, and raydric archers.
So long as your team knows you cannot cast Angelus, Gloria, kyrie and suffragum (if you build your priest to cast two you can't cast the others). Your skill points are very tight, you'll be level 37 before you're done with ME and those other 13 points can be very precious, either safety wall or kyrie will eat up 10 leaving you with a whole 3 points remaining. Plus you don't have the vit to be a tank, if you get any vit your cast time will take a hit.
Still, you can always level by supporting others. So if you run out of money to buy blue gems, go look for someone to support.