I implemented real-time health bar updates (from combat log) within Grid itself so it cannot possibly interfere with operation of the built-in or other add-on mods. You have to enable it explicitly in the configuration for it to activate, and then you can see some running statistics via /script GridStatusHealth:EstimateStats() after it's activated. It seemed to work fine for the weekend (including healing our first Felmyst kill last night) so I'd say it's satable enough for other people to give it a shot.
Get either patch or full Grid replacement here.
Edit: The computer it's hosted on went down, here's another place with the patch for download:
http://pastebin.com/m5050bf59