Spoilers: It falls significantly behind.
This was done by smashing the melee button until five melees were performed with each class. The more melees you do, the further behind warlocks fall. This is a pretty egregious issue considering all classes have the same melee range. It means you are out of luck the moment you engage in a melee fight with anyone except another Warlock.
But no enemies are being hit in that video. Does this apply to actual melee fights?
The answer is yes.
Will this be fixed next season?
One can hope.
Edit: For the nth time, all classes in D2 have the same melee range. Handheld Supernova is not a melee.
In case the links don't work, u/pisshorse made gifv mirrors.