Have you survived all enemy waves? Yes
Have you enjoyed the fight? Yes
Difficulty level: Insanity
Shepard's class: Adept
Weapons used: Tempest, Vindicator, Phalanx, didn't touch HW
Bonus power: Heavy Barrier
Strategy
Basically did the entire fight from the piece of cover up against the back wall, behind and to the left of where you start the fight out, looking through the posts it seems like many others have discovered this spot as well. You're completely covered from 3 sides and nearly covered on a 4th side, essentially can't be flanked, and have a great angle from which to toss your powers out to anywhere on the field.
My basic pattern was to start with Heavy Singularity to lock down one enemy, while it was draining his shield I'd pull a guy at a different spot to stagger him, take out his shields with gunfire (Vindicator for guys across the room, Tempest for those closer up), pull again, warp bomb, wait a few seconds for CD and shield regen, turn to guy who was locked by Singularity, see that he is now floating around as Singularity took out all his shields while I was doing other stuff, warp bomb again, clean up anyone who got owned by warp bombs with gunfire (if they have only a tiny bit of health left) or another pull/warp combo (if they have most of their health left). Rinse and repeat with liberal applications of medigel so that I can lean out of cover more (and thus spam powers more).
For elites and pyros Heavy Singularity + a couple Vindicator bursts takes out their shields at which point they're no more threatening than the normal mooks. Just making sure that Shepard is snapped into cover when flashbangs go off prevents them from staggering him, and the blinding effect does nothing since precise aim isn't required for this routine, you just have to look in an enemy's general direction to hit him with powers.
I had to reload a couple times trying to run from the YMIR, but then I figured out that if you stay at the back left corner spot, he actually won't circle around enough to flank you; he comes very close, but stops just short of being able to hit you while you're snapped into cover at that spot. So my strategy for him was the same as the rest of the fight, camp at that piece of cover, lean out to shoot when there was an opening, cripple/kill with biotics after stripping protections. The only issue was that the YMIR's missiles would stagger me from exploding against the wall behind me, but since it's already hard for enemies to hit Shepard at this spot and the YMIR itself blocks most of the small area from which they can hit you, the staggers weren't fatal and I was able to just snap back into cover afterwards. Barrier served as a safety net, preventing death if I messed up and let a flashbang stagger me, or if a pyro snuck up on me; 200% shield regen was also useful to let me stay out of cover more often against the YMIR (and thus pump more Tempest clips and Phalanx headshots into it, and thus kill it faster).
Feels kind of cheesy using that cover spot, but Bozorgmehr's video demonstrates that you can go elsewhere and the enemies still don't know how to flank you (and as he noted, if they did know how to flank you, it would be nigh impossible for an Adept anyways), so meh.