DPS Meters are ok on encounters with usual tank&spank and low dps movement. Best use for DPS meters is on a raidpuppet unbuffed so you get a hint, how well you can perform with dps only.
And it's a good way to see, if you do enough dmg for some bosses.
For the Healmeters, well ...
When I spam Healing Wave on you, I'll be on top with massive overheal. When I spam CH and Heal Totem, ill be even more on top. So Healmeter don't matter.
A Priest casting shield on tank > no dmg > no heal > bad for hps. You can't use hps meters for heals - it's nice to know how much you could do or how a new trinket benefits you, but it's just not usable for raids. Because theres movement, groupheal, manasaving, dispel etc.
On a high movement fight I (as a shaman) have big problems with my casting times, riptide is nice, but well - only one small hot :3
Druids just hot the hell out of the raid and would be on top :P