Good question. I just leave them at default myself, and I've noticed it spends an equal amount of time healing itself and DPSing, so it looks sort of strange. I'm no good with settings unless it's a "Click to enable or disable" type of setting. If there are percentages to be placed I generally fail to comprehend them for some reason.
I'd like to see some sugestions for Raid, Instances, Soloing, Questing, PVP, etc. I know it's a lot of work, and I'll probably just play around with the settings until I find something that works for me, but like the OP said, would someone mind sharing some options?