Morrigan is definitely a good character but because she depends on assists to really build meter for herself and do good damage without level 3 hyper or xfactor, i would put her in the B range.
I can honestly say that she is one of the best if not the best runaway character in the game. due to her flight cancel, she doesn't have to be stuck in recovery time. that's a huge plus for her.
unfortunately she's not a very self-sufficient character though. even in astral form it takes a lot of work for her to gain a meter without assists or xfactor yet she depends on meter to kill.