Daggers are the required weapon for the Scoundrel weapon abilities, however, they are noticeably weaker than their Strength counterparts. This results in the Rogue (Daggers+Scoundrel) playstyle not being very rewarding. I'm not saying one can't play Rogue, and I'm not saying one can't beat or even solo the game using Daggers, but I am saying doing so is harder and with no apparent rewards over alternatives.
This issue primarily stems from that fact that Daggers have a lower base damage than Strength weapons, but without any apparent advantage.
As an example, a level 5 dagger will have a base average damage of 26. The corresponding 1H Strength weapons will have 38. That's 46% more base damage to the Strength weapons.
In an attempt to offset this, one might consider picking the Backstab talent (only works with Daggers, and all attacks are crits if done from behind). Since crits do 50% more damage, and we can (theoretically) Backstab for all of our attacks, our damage is now on-par with the Strength weapons.
However, getting directly behind the target requires extra effort and isn't always possible, all of our crit strike stat is now wasted (Backstabs cannot also crit), and we have spent 1 of our precious talent points just to be on even footing. This is a huge cost to just do the same damage as a Str weapon user would by default.
Also, because Backstabs cannot crit, and it appears that Backstabs are an important Dagger mechanic (as evident from the auto-backstab included in multiple Scoundrel abilities), there is an anti-synergy with the critical strike granted from the Dual Wielding bonus and the Wits stat, both of which are core to the standard Rogue identity.
This doesn't even address the fact that the scoundrel weapon abilities are all limited to 1 target and do not provide any CC, while the Strength based Warfare abilities enjoy these bonuses. However, perhaps those abilities are just too strong.
I would recommend 1 of 2 changes. Either increase the base damage of daggers to be equal with Str based 1-hand weapons, or make Backstab a built-in dagger feature that can occur alongside a regular crit strike (This would STILL be weaker than Str weapons as getting a backstab is effort that should reward with higher damage, not just equal).
If daggers were also granted a higher base critical damage bonus that may also help with their identity and balance.
Without the damage potential being equal, why would anyone use daggers and the Scoundrel weapon attacks? I believe in DoS1 the daggers had a lower cost to attack, which is why a lower base damage was acceptable, but this is no longer the case.
Off-topic a bit, but the Spear doesn't have any identity. It requires Finesse, but doesn't work with Scoundrel abilities and the Warfare abilities don't scale off of the Finesse. Spears do have a slight extra range bonus, but there are no weapon abilities which they synergize well with.
