DPS is DPS no matter how you cut it. Burtgang is a slow weapon that needs a crappy WS, at 300tp, to get a, non-refreshable, aftermath.
Excalibur has better DPS. Faster WS, more WS, ODD proc that doesn't require aftermath, and a fairly potent added effect. It looks to be the best sword in the game depending on how delve boss weapons turn out.
That said, Burtgang is pretty broken for tanking now, post tanking adjustments.