Brian, i highly recommend trying the N7 Typhoon. It's damage may not seem very high and it takes a second or two to fully wind up but once it gets going it shreds like no other. Plus it has an innate armor piercing ability
Make sure you do sanctuary main mission before doing the citadel dlc because your still missing one person to be apart of the citadel dlc and Also there is a method to scanning systems that makes it so much easier to get what you need just go the system back out of galaxy map and make a save.
I've suggest you to complete Horizon mission after DLC's and leave Citadel's one on the last (I mean, after Horizont), cuz then you'll assemble the whole team (Including Miranda). But It's only my advice, you could complete as you wish.