Your DoTs are too slow against their burst - Fear/Psychic Scream on the Rogue's engage rather than trying to trade early.
Kite when possible and keep DoTs rolling on the healer to punish any overextension.
Two DoT-heavy teams - whoever lands Fear/Psychic Scream on the enemy Shaman first usually builds the lead that decides it.
Long grind favors your DoT uptime - Earth Shock the bigger heals to slowly pull ahead.