I like the 2.5 second GCD. There are lots of subtle ways in which the constraint makes combat more interesting to me. A longer GCD means a greater cost or punishment for making a bad choice.
Please don't change it S-E. Plenty of other MMO's have gone the faux-action route. Stick to your oldschool roots - it's obviously applied to 100's of 1000's of players. :)
