I like macros. I am not an expert, but I don't suck at it. Try:
/castsequence reset=121 Blast Wave, Arcane Explosion, Arcane Explosion, Arcane Explosion, Arcane Explosion, Arcane Explosion, , , , , , ,
Just put in seconds the cooldown of Blast Wave for the reset (I add 1 sec to make sure the cooldown clears and I don't get "Not ready" error).
Hope that helps.