Looking at who's at the top of Skada/Recount in most top guilds streams/kills tells me you're wrong.
Either that or all 4 Warlocks Method, Blood Legion uses are lucky every single time.
Epeen Bot also has stats which DPS is needed to reach the 50th, 75th, 95th percentile for each spec+fight. Sounds like a good indicator of "who can do the most damage every single time, on average".
http://raidbots.com/dpsbot/Immerseus/25H/all/14/30/p75/
http://raidbots.com/dpsbot/The_Falle...all/14/30/p75/
http://raidbots.com/dpsbot/Norushen/25H/all/14/30/p75/
http://raidbots.com/dpsbot/Sha_of_Pr...all/14/30/p75/
http://raidbots.com/dpsbot/Galakras/25H/all/14/30/p75/
etc.
I also think that Warlock has a higher skillcap than Rogue or Mage for example. And very powerful utility for the raid and surviveability.