According to what I've been reading, most prefer a mix of multi, crit (and mastery, but not at 19)
One point I notice may have been missed or misunderstood here is this.. a sub rogue does not do sustained dps. If you want to do sustained, you go combat. Sub rogues are your assassins. You hit, you git... So to that end, I stack on agility, attack power, crit and haste. I would prefer elemental force x2 as my weapon enchant, but any enchant with +agility or +damage or +crit would work.
Basically, your enchants should be adjusted to your playing style. I play subt, so I want in fast, do max burst dmg, and out again. I also stack a lot of haste, so my weapons strike as many times per minute (usually per 15 seconds) as possible to apply poison dots, and extra elemental force procs.
Keep in mind, at higher levels, haste is not as useful as it is at lower levels. The best test of a build I can think of, is pick a restro druid and try to kill it.