They're pretty effective; I had one in my game pretty recently.
The most brutal trick was Hammer Rhythym + Brutal Barrage. Its minimum damage with Aug 1 was 24, and its max was ... well, usually 24, but with four chances to crit. Two hits knocks prone, making it remarkably effective at keeping an enemy in place. The only problem was, he got kind of repetitive.
Mind Blade pwnd one of my Elite enemies. With a follow-up Action Point + Brutal Barrage Aug 1, it made me sad. Yes, there are more dangerous combos out there, but Unconscious (Save Ends) is just plain gory.
His PP gave him a Level 12 Utility At-Will which turned out pretty interesting, actually, for when he was very hurt. For a Standard action, you get to save vs. any attack. A successful save reduces the damage to 0; failure still cuts it in half. The important note here is that it doesn't prevent you from using Lightning Rush that same turn, nor does it prevent OAs or your Mind Spike.
Speaking of - he only used his defender whammy once, and it was okay. I think it will be a LOT more useful now that monsters are dealing more damage.
-O