Dumping int is a bad idea with rogues, it kills the damage from deep wounds as the duration is modified by it.
Deep Wounds is overwritten when you hit again regardless of duration, so if you're a melee rogue that's probably a non-issue
What this guy/gal says. You can and will apply deep wounds over and over and over and over and over. Even with 3 int you'll never see it expire.
(unless you're screwing up really badly )