Mass-effect – Was there a way to prevent Morinth from turning into a Banshee

This would most likely stem from two things, from Mass Effect 2:

• Shepard's assumed association with Cerberus, a group who has its hands in many less-than-respectable activities.

• Shepard's assumed liability in the deaths of 300,000 Batarian civilians at the end of the Arrival DLC, which threatened to give the Batarians an excuse to wage war against humanity and weaken support for the human race from the other Council races.

  This outcome is hinted at in the dialogue with Admiral Hackett at the end of the Arrival mission, in which he reminds Shepard that [he/she] would be a convenient scapegoat to avoid war and that "when Earth calls, [he/she] be there with [his/her] dress blues on, ready to take the hit."

My strategy for the Banshee is fairly class agnostic.

First, try to wipe out everything else that you can, so that you're down to just the Banshees left. This can be tricky, but they tend to move more slowly at first than other enemies, so if you put some distance between you and them, the other enemies will rush you and you can focus your fire on them.

Mostly my strategy is to run. I run like hell. The Banshee's really only got a couple of attacks. First, don't let them get close to you, and second, keep enough distance that you can rapidly turn a corner if they throw their warp projectile at you. Then it's just a matter of wearing them down. The heavily armored, so use whatever anti-armor gear/powers you've got on them. Their barrier recharges relatively quickly, but it's pretty weak by comparison.

Getting hit by their attacks not only does a ton of damage, it also causes you to take some damage over time. Prioritize getting enough ground and cover between you and them to block their ranged attack when it comes. If they start teleporting, just start running.

I try to train the Banshees myself, and keep my squadmates alive and focusing fire on them one at a time. My squadmates really couldn't tank the Banshee worth a damn - they tended to go down quickly if it focused on them. If they go down, do a couple of laps of your arena to get some distance, and you should be able to spare enough time to get them back up again. Having maxed out medi-gel so you can just instant-revive them and/or recover your own health is a plus.