Would be a nice feature for those that want it. Personally to me it is micromanagement of something that I do for fun and I wouldn't use it.
As far as Damage stats if your going to look at anything. Go check out a mod called Recount (its on wowace
http://www.wowace.com/wiki/Recount ). I played a warlock as my main character for a long time. One of the things I love about Recount is that it doesn't just say who had high dps and heals but it breaks down things much more granular. Healers will be able to open a graph in game that shows a break down of healing by spell type. For your hots it will show the % of time your hots were up on a target. For DPS it breaks down your damage by ability. It is a really good tool for people to look at and see where the majority of their damage or healing is coming from and be able to maximize what they are doing.
Now if you are going to use things like this on a site I think an importer based in Recount would be wicked because of the detail of data and graphs it already has. One other cool thing for raid guilds is that it can track who is breaking CC. Most of the time this should be a Tank. So if you have problems with people that multishot sheep then Recount can give you data you want to see.
