Its possible m8,I guess the only thing is to try it and see.
I'd like to add tho you might want to consider levelling both teams on rested XP,i.e When your DK's XP bar goes red,swap to your Shammies.
I really regret not having my Shams done before or at the same time my DK's dinged 80,sometimes Melee teams can get frustrating so now I can swap back to shams for a change ;p
GL with your teams.