Had a chance to rock with all 4 classes...and The Colossus by far was the most difficult to play with. They really need to fix the shield mechanic....he should be able to attack and block simultaneously, not one or the other.
Another issue with Colossus is when shyt gets thick, that manual shield gets eaten alive and then youre back to face-tanking
The Colossus has no real way to cover its 6 becuase it moves too slow, so your flank is a huge liabilty. All the other classes move fast enough where they can negate that.
The only thing they got right with the Colossus was the offense/attack because that machine can pack a punch and really knock iff chunks of a bosses life. Only adjustment I would make is shorten or even eliminate the cool down on The Colossus' melee attack. He should be able to spam that move as a defensive mechanism as well as offensive to keep enemies up off his slow ass.
The other 3 classes are all piff tho.... The Ranger feels like Iron Man while doing his ultimate
The Interceptor moves great and his triple jump move plus his unlimited melee attacks are
And The Storm is damn near OP with his freezing attacks and defensive hovering + force field