Actually i'm not sure Corvettes have the best DPS, given the numerous reload times (and the fact you have to evade once reloading).
They have the best primary's burst damage, for sure.
Destroyers and some dreads (oberons) with their big clips are probably flattening the damage curve.
There is also the fact that the potential module burst or dps is significative from a class to another. (See the dread scattergun broadside dps for example).
Isn't the JupArm dread primary bugged at the moment ? Like halving damages ?
I've been told the mortar turrets are pretty awesome too (didn't get there yet).
Speed can be gained by judicious uses of energy gauge and slow timer warping.
Of course there isn't a ship that is very good at everything...
For what i'm seeing, EXCLUDING modules/secondaries (there are some against two or three classes in each class), each ship class is meant to be effective against one other class, and itself; destroyers are the less pronounced counters of all and slightly better against everything (technically they seem to be geared against tacs).
Dreads are destroyer counters and fare well against other dreads.