i'd argue that area energy drain is a better bonus power for a vanguard on most missions
enemies usually occur in groups, and those groups always have defenses, and a great deal of the time those defenses are shields.
charging into those groups is the cause of 90% of vanguard deaths, according to the latest research.
what i do now is sit behind cover for a sec, hit the group with area energy drain, then charge on in. why is this preferable to leaving their shields up? well, the first guy you charge you can basically forget for the next 5 seconds. he's sent flying. now you can turn to the rest of the group and deal inferno ammo damage to them that's guaranteed to trigger the panic animation ON THE FIRST SHOT.
your shields are full, and you haven't spent valuable seconds finishing off the dude you've charged - seconds where all the closest enemies have a chance to draw a bead on you. so basically your heavy charge's slowdown can be spent getting the jump on the rest of the group. i've actually had charges using this technique where no enemy got a shot off, and my shields stayed untouched.