Except for the part where you don't.
Maybe he means on PTS, or on Fabricator, or on Kephess the Undying.
In any of those situations, 2400 is entirely believable.
Otherwise.... no effin' way. No class reliably sustains 2400 DPS on any single target without boosted damage taken.
Unless he's talking about burst DPS, in which case 2400 is hardly noteworthy, and PT, Marauder, and Sniper would all like a word with him.