Many ground combat scenarios are taking way too long. 30 minutes to bring down one group is too long. It seems to be random as to which encounters are like this. The shield bars on the enemies are sliding back and forth and when you have one of these out of whack encounters, almost every enemy combatant heals up 100% as soon as his health gets too low.
I am not saying they cannot be handled, because eventually you can wear them down, but it is taking way too long. This only started happening recently. Within the last couple of days.
I don't even bother with ground combat anymore...I just run through and head right for the objectives, fight what I have to to quickly get a scan off on it, then move on. It usually ends up being much quicker, but there are times when I have to fight a huge group that follows me around, but even then it's not usually a problem.
Ground combat is broken and boring. Take advantage of it.
I've run in to groups like that. Be on the watch for multiple medics/scientists in the group. If you can, try kill them first (tell your team to attack your target) and the rest of the group should become easier to take down.
I have to ask what difficulty setting you are playing on. Until I hit LT. Cmd. and bothered to turn the difficulty up to elite, I was blending through all the enemies I ran into, with the sole exception of the Kuvah'Magh mission since it constantly respawned enemies.