This is a truly good roguelike, especially for a web-based. It gets a rare 5 from me.
The strategy I'm using through Hardcore seems to be working well: 2 Clerics in front (all points into END), 2 Mages in back (all into INT). Just make sure the Clerics are faster than the Mages and Anoint+Electrical Storm, Anoint+Electrical Storm. I just beat the Corruptor and I have yet to let a character die.
This game shows a surprising amount of depth. One suggestion I have is in Free Swim to show the score for the current combo. It could appear in the usual corner and then fade.