Personally I think he is underrated and provides a lot of utility for the team.

• His molly does lots of damage and is amazing for post plant lineups.
• His smokes are cheap, pop instantly, and they last FOREVER. You can lock down one entrance to site for almost a whole round.
• His stim beacon is great for quick takes and rotates.
• His ult is one of the best in the game and can get you a guaranteed kill if you use it right.

He is one of the best controllers, maybe second to viper, and should be picked more often.