So I did some testing of my main hypothesis, that Enchanter is OP because channeling isn't working right.
On a level 1 Druid with 0 channeling skill I was interrupted every cast. No chance to channel. I then went and put 1 point into channeling.
Out of 30 channeling skill checks, 9 were interrupts, and 21 were successful.
Just some starting data and final channeling skill was 9. Level 1 channeling is ~70% successful? Seems a bit off, I'll do more testing.
Also something interesting I noticed which may just be random given the small data sample is that if I was fighting on a hill where pushback seemed to move me further as I slid down the hill my interrupt rate was higher than if I positioned myself to be pushed uphill. To avoid this I threw out a couple samples and only took data from flat terrain. Data gathered may need to be while positioned in a corner to minimize push interruption vs hit interrupt chance.
http://www.angelfire.com/nt/com1/playg.html
Lots of player comments that dexterity impacts chance to regain concentration. This link seems to support that as it was an official document.
"Dexterity:
This is your hand/eye coordination and is used in combat accuracy and spell casting capability. This is used in calculating your missile combat skills and aids in determining if you are interrupted when you are hit while casting a spell. "