I always used to spam my Buttons 6 times a second if I panick in an instance for whatever reason there may be and so I set all my click macros up to 6 sec-spam (aproxx. of course) and the DPS is really fine.
I still got a long way to go but killing the herold in 15 seconds was my best until now and I hope I'll be able to improve that further.
Never came close to such numbers with my other methods and not to talk about playing something else than shamans - I got a warlock in my team and it's so comfortable spamming just one key knowing that all my toons work at a 90+% efficiency.