Dragon Age 2 happened which made me doubtful of bioware's quality.

Note the Almost. As in almost essential, but not. In wow you could heal just by typing, in fact that's how I healed in wrath of the lich king. It is just very handy to have a mouse over option.

You're right, mouse over casting is incredibly handy and almost essential, and they should add it in the game, not just for healers, an instant cast crowd control spell on mouse over has saved groups countless times. It won't deter me from rolling a healer once I get in, but I'm sure someone will die because I need to 'readjust' to the old ways.