I played an Adept run on insanity from ME1 through ME2. The Adept is far from weak.
These vids are not mine, they will contain spoilers in ME2. Watch at your own risk.
http://www.youtube.com/watch?v=8MaZ2Z09naM&feature=related
http://www.youtube.com/watch?v=qrZb2h3gte8
http://www.youtube.com/watch?v=i8yPvaSLRWc
EDIT : I done the same with the Vanguard. That was my fav char type.
Pfft, that's weak bro. Would have had that [censored] done much faster as any other class. Not to mention it falls into the SAME trap of singularity/warp spam. Oooo so awesome and unique. Seriously why do people delude themselves into thinking the Adept is an equal. It's not. So boring bro, I miss the days of Mass Effect 1 where you coud use all of your powers. Your whole thing was crowd contorl and it worked. Now its singularity warp spam. It's so debased from the original badass I feel sorrow. Every other class can apparently be overpowered or have an overpowered move. but oh gods no, not the Adept. Lets design him to just scraqe by, and require the DLC packs to becoming even slightly closer to being an equal.
Soldiers are pure survivability and carnage damage. By far the best class in the game because of how versatile they can be with ammo and guns.
Engineer had great powers.
Vanguard was tough, but rewarding if you could master it. The charge thing was pretty insane. I hear it's a steep learning curve though.
Sentinel has the best and most adpatible array of powers. Just awesome. Not to mention tech armour which was amazing.
Infiltraitor has early acces to snipers which helped with tons of enemies provided you were a good shot (which I was). And he had cloak so he could get into and out of situations at will.
What do all of these classes seem to have? Versatility and adaptability over and above the Adept. Now in ME3 some of them are even stealing the Adept'ss thunder and getting control abilities that presumably work against shielded enemies. So wait what's the point of the Adept again? Anyone feel like reminding me?
Edit
I beat the game with nothing but pistols on Insanity and singularity/warp. It felt like cheating with the mattock and by the time I got stasis I was so awesme at warp/singularity spam I just didn't really need it. Though I did do a fun run through with the mattock once too.