With the exception of specific endgame fights, cover really has no use in everyday fights. 99% of the time that you lose hate you can get it back immediately with provoke faster than you could use cover to target your ally. I imagine a large number of tanks have gone through the whole game and used Cover less than 5 times. Right now the skill is rather pointless because there are other things you could be doing that have a better effect instead of spending your time covering someone.

I see no issue to letting cover work for anyone near you. Its a slight buff imo for an ability that never gets used. Its not game-breaking in the least.