This is a huge issue that gets to the crux of the current state of casters.Nope. Casters DPS always lags behind both melee and ranged even in heroics. The big difference is they kill groups of mobs in a single cast and it makes them FEEL like higher DPS. This is why they feel so bad in high level epic/legendary because they can no longer 1 shot/2 shot mobs.
If the enemy has 10k hp and caster does 10k damage in 1 cast with a 6 second cooldown the DPS is 1667 but the mob instantly dies.
If the enemy has 10k hp and a melee does 2k damage per attack and 3 attacks per second the DPS is 6k but the mob takes 1.7 seconds to die.
Casters have damage break points and any monster that surpasses that breakpoint makes a caster feel gimp because of spell cooldown.
In the previous example if the caster does 10k damage and mob has 11k hp it takes a caster 6 seconds to kill a mob as compared to their previous instant kill while the melee's time adds 0.3 seconds to a total of 2 seconds.
Look at something like haste boost and how it multiplies melee dps. Casters get what?