I duo using cover. It's definitely not a lifesaver but it does work. When duo'ing I line up close, and my partner is right behind me. If she yanks too much hate; or, in it's infinite wisdom, decides it's her turn to get mashed, I pop cover and it helps a little. I imagine it's going to end up much like PLD cover in XI was. Useful in odd small group situations; but you'll never end up building a major strat around it.

Sidenote, the animation rarely plays for me when I cover. Maybe... 1/3 times?