Hi, i cant aggre you about mage/scout. Because it doesnt have enough AoE damage for big pulls. When your tank pulls high amount of mobs so often, you may underperform with that class (just my opinion). Scout/Warlock also doesnt have good sustain. In some situations you might miss some damage. I think you should put scout/warlock to C and bard/mage to A. I had a very good experience with bard/mage in grafu. Its AoE sustain damage was good enough.
However, this is just my opinion. I dont know how your guild runs grafu. Your guild's gameplay and my guild's gameplay might not be same.