Ok,
As a endgame Mage here's my thoughts (and they fit with everyone else's)
1. Pvp omg you need heal ( I personally use fb, light,shield and heal)
2. Pve do not and I mean do not have heal in your skill set at all, pve endgame you mash pots for heal and mana (so buy lots) and as others have indicated you should use 3 attack skills and shield for elite maps