As far as in-game mods, I'll recommend Recount.
I did not realize it is no longer maintained.
The version I have works very well, and is easy to configure and use.

I'll definitely check out Skada.
There's a good chance a fan based update will keep Recount going indefinitely.
Most of the popular addons are maintained this way, if the author quits.

Something like Wow Web Stats or World of Logs will get you much better information.
Essentially they will parse your combat log, or multiple logs for a more accurate assessment.
They give a lot of very useful info which you cannot get from an in-game mod.
Of course these, you view on a web site, outside of game (or Alt-Tab'd out).