I was just able to get it down to 4 minutes and 32 seconds with slightly better execution- even though I died once to skeletons. I'm sure a run hovering around 4 minutes is possible.
EDIT: This strategy is no longer viable in 0.0.6 because the Draginslayer was replaced by a plunger. Well, it was bound to happen eventually. Still, I'd like to see other times for the 0.0.5 version if anyone's got some.