you should be fine with this combination.
i would suggest trying to map the first six buttons to your warrior and give him the most real estate.
give some totems and attacks for the shammy on four buttons. give the shammy a follow/focus all in one button. and finally, give the shammy a heal button.
you should be all set. this is two boxing, so use the warrior the most with the shammy for heals, dps and buffs.

good luck!