I was always a fan of assassins wielding 2 daggers, but in gw2 playing double daggers on Thief is more punishing than anything. Skills 2 and 5 are great, but skills 3 and 4 are a big waste of space and feel very outdated. It would really help if you added Quickness to it's kit, for quick burst and a survival skill. Not to mention, the only usable elite skill is Dagger Storm..
Thief's utility skills are great, but it's sad that you need to use those slots for condi cleanse, stun break and shadowstep and the cool skills like Assassin's Signet are never used.
I have all expansions, but still love the core thief and I wish the true double dagger assassin will be viable someday