I was thinking about something like that sometimes ago, but to be honest, I didn't found a good way to do this, mainly because I dont exactly see the point.
I made WowCardio, because I was unhappy about all existing parsers, which focused on stats, and never show what happened in real.
With those parser you could compare dps/hps, but nothing else unless it's the exactly same fight: Because comparing 2 players is very situational in fact.
I mean, a player is good because he does the right thing when he needs to. If you try to compare what a player does in one fight, versus what another player does in another fight, this may be quickly pointless.
But maybe I am wrong...
However, WowCardio has a very rough compare tool, based on the raid Dps/Hps histogram.
To use it go to the "Compare tool" panel at the right, And right click in the White panel, and choose "add Raid Line"
all current raid line will be added in a list that can be save for a future usage. If you check a line it will show in the Gfx view.
For to save a specific raidPlayer, you just have to toggle "focus" on him, and choose the focusmode "source-event" only. Then the raid line will only use this specific player datas. After that you can easily compare general hps/dps within other player.