I made a dagger user without Backstab last patch. Some Scoundrel abilities can Backstab even without the talent (Vault and Throwing Knife), and Backstabs cannot also crit, so they don't stack with Rage.
If you decide you want a different talent (or hate the inconvenience of getting behind targets) you can cover for Backstab with Rage instead. It makes it a lot easier to also incorporate certain powerful Warfare abilities that are difficult to Backstab with anyway, namely Battering Ram and Crippling Blow, etc.
This build would mostly be better off stacking Strength with 2 Strength weapons instead (especially since weapon abilities no longer double dip from mainstat) because Strength 1 handed weapons have higher base damages than daggers, for the same cost. For example, a lvl 6 dagger has 11-12 base, while a lvl 6 Sword does 14-16. (30% more average damage to the Sword)
However, using daggers gives access to Vault, which is pretty good, and also Mortal Blow.
So, the trade-off to use Daggers w/o Backstab is basically 30% damage lost (compared to Swords), and the only advantage is gaining access to Dagger-only skills (Vault, Mortal Blow, etc.).
Of note, the damage difference was reduced this patch (used to be 50% more using Swords, etc.), so daggers are not as bad off as they were, but Backstab is still mostly essential for Dagger using to be competitive (a sign that it should probably be a default feature of Daggers and not a talent at all).
If we assume that Rage is too dangerous to use, and that a character will be able to easily Backstab 100% of the time, Daggers will do 1.5 damage vs 1.3 damage compared to Swords. This difference is increased much more for higher quality daggers that have an increased 200% critical multiplier.
In summary, I would not recommend using daggers without Backstab. Just use Strength weapons if you hate backstabbing, but it's probably not bad enough to be nonviable.
However, using Backstab in conjunction with a good 200% critical damage dagger seems very worthwhile now.
I still dislike that any extra crit chance is mostly wasted on a Backstab build though, since Backstabs are already guaranteed to crit (thus greatly reducing the usefulness of Wits).