I would suggest putting your healing sequence on a different key than your dps sequence. Its the only real way to control it at a different pace. Alternatively, look for a spell with a cooldown that you can put into the rotation that will throttle the sequence. I use prayer of mending on my priest to ensure my renews are staggered:

/castsequence Prayer of Mending, Renew, Prayer of Mending

Prayer of Mending has a 10 sec cooldown, Renew last for 15 second, so tank goes without a renew for about 5 seconds. This is from memory, but I think those numbers are correct. I don't know if Druid healers have a similar spell or not.