I played Vanguard thinking it will be diffrent from soldier from ME1 but in the end i didn't even have to use those biotic powers too often as the hard difficulty was so easy.

Did you play on PC or Xbox?

Xbox 360.

I have a Lvl 30 Soldier from my first Runthrough and another Lvl 30 Adept that was my personal favorite to play with

What gets me in ME2 is how much they nerfed the biotic classes, most notably the Adept. I still have a level 20 Adept sitting around in ME1 and it is unbelievable how Godly she is in terms of crowd control. I just hit singularity, 5 enemies regardless of whether they are in cover or not instantaneously float around like pinatas and they get blown to pieces.

In Mass Effect 2, playing as an Adept feels a lot more down to Earth as in a mole in a molehill. I throw out a singularity, the enemy ducks and I am left with a blown cooldown and no dice.

Shame, shame, shame. I really like the Adept and I hope in ME3 they give it back some of the prowess it had in ME1.

You definitely need to try it out on the harder difficulties. I played my first run through on Hardcore and I thought it wasn't too bad once I got used to it. Then on my second (current) playthrough on Insanity, I was getting tore up, because you die so fast and the enemies are much harder to take out. I guarantee that it won't be the cakewalk that normal difficulty is.

As for the topic: I'm an Infiltrator (Widow FTW!) and I love the class. Cloak, then come up for a sniper shot with the Widow and POW, destruction! I went through on Hardcore as an Infiltrator and I'm doing a new game on Insanity with my Infiltrator. I really need to continue my game as I got side-tracked by other stuff (Alan Wake!)

Soldier, though it's a lot harder than the first one.