I've done a bunch of different two person teams (wish I had time and money to make 5 since it is so fun ) and for shear ease of use I have to say my enh shammy/ele shammy combo was the best. Having rezzes plus self rezzes along with 15 minute hearth plus RAF summon made them go very very fast. It was pretty easy to have the enh shammy tank a mob too while having the ele shammy blast it. Not sure if two pure casters would be more efficient but it was lots of fun and 60 came faster than I ever thought possible.

The bottom line though is to try out all kinds of different characters that fascinate you and have fun with them

Good luck

D