I'm not sure I follow when you say "only one range enabled". What other ranges would be enabled? I do run other range AddOns (I believe Quartz has some range finding), but Grid is the only one that sends the CPU utilization up. Could something have changed on Bliz's side with regard to range checking?
Part of the issue may be related to me not playing a healer in AV in some time. I had stopped for awhile while I leveled my druid to 70. Now that I'm there, I'm running a lot of AV and it just seems worse than before, but I'm not sure how far back something could have been changed.