Only if you have no idea what you're doing.Engineers = Everyone's friend in multi. Chain overload stun someone, turret support. Love it. Its my fave class because you worry more about helping everyone out then just spamming biotic charge to kill people.
Infiltrator = Guardian Angels. Probably my 2nd fave class. Geth Infiltrator, Black Widow - cloak - BOOM. one shot pretty much everyone even going through guardian shields.
I also like the Drell Adept. Since i havent unlocked a proper Asari Adept yet i use the drell and its fairly fun. Pull + Reave = Boom. or Reave, Grenade BOOOOOM. Best way to clear a choke point or an enclosed room.
Vanguard: Fun to show off in front of people on bronze. Only good if you have someone really good backing you up.
Vanguard's are pretty damn near indestructible all the way through Silver. With a little passive help like a Geth Turret on Gold, they become truly immortal.
But the world is full of shitty, get ko'd by a phantom spamhards.
Also, Geth Infiltrator was made for the Claymore.