Ah, this is why. I don't have Biotic Charge set up to recharge. I can use Nova twice in a row, but normally end up getting impaled by a Banshee if I get too close. Killing them usually happens when I run and then blast them from afar and use my missile launchers.
Multiplayer is 50/50. 50% chance of ending up with a ponce team. During a game with people higher in level than me, they all died leaving me to fight off a Brute and Ravagers alone. I survived that Wave by meleeing a Brute as it was charging me. Then the next Wave I had to do the same damn thing cuz they all died again. I survived that too. Then at the ninth Wave everyone died despite the fact that they could have revived one another on multiple occasions. -_-
Finally after getting put with ponce public teams, I got put in a really great team with a Krogan, Turian Sentinel, and Infiltrator. We did quite well. Of course it helps that the Krogan had a grenade launcher and I had a Scorpion Pistol and missile launchers. Krogans work very well against Reaper forces. Meleeing the crap out of a Brute has only worked with a Krogan. When I try that with any other character I end up dead.