Thanks for all the replies. Based on some of the advice I've received I've now decided to level a 5 man team of shammies. It seems a tank and 4 shammies is the best set up to run heroics, both in terms of setup and being easy to multibox. Once I have all my chars geared up I will try my idea of a mixed class heroic group made up of the 4 tanks classes and a shammie.