Bah, what are 7 levels of difference anyway ; )
Dessi Mages still kick major ass, even at higher levels their power doesn't have to hide behind the other classes.
A high level Dessi with his magical +9(that's equal to mastercrafted full-plate for gods sake! It starts to get really sick when he decides to additonally wear a real mastercrafted full-plate on top of his magical protection = 28AC) AC bonus and equipped with his magical boomstick, which grants him a combat skill equal to a Sommerlund Knight...besides a 18-20 critical threat range and triple damage criticals, is a total melee monster.
With his attacks easily able to get to +25/+20/+15/+10 and every hit dealing 6d6+5 he can mow down pretty much everything in a few rounds and with additionally battering his enemy with Psychic Combat(and if he gets a critical you can already order a coffin, because that's 18d6+5 coming right at you and the resulting average of 68 points of damage means you'll have to make a fortitude check against a 33DC to avoid instant death).
While it probably isn't too much in character for a Dessi to run up to a horde of enemies and start beating them to a pulp with his staff(not to mention wearing full-plate armor while doing it...), it certainly is very effective(and Grey Star did it all the time, ok without the full-plate armor ; )