Hi, I have the same prob when I'm in P/S (video on youtube at rofl, inferno etc...). I use addon Grid, I don't have raidheal and my fps drop radically. I have 110 fps with nothing in my house and when I use urgent heal, heal arrow or chain of light, I have only 20-30 fps. My pc is good (2 years)
My last test is in Druid/warlock tank at DN, when I use recovery on me and when my priest use his macro for healing me with urgent heal, I have a brutal fps drop with big freeze. I got a lag because all my alt's account are connected on the same pc, I put the video on youtube today.
I will test your addon and compare this on rofl and I hope it's better 