Scepter/dagger-focus...
That depends: do you want to have more damage or more survivability or a combination of both?
My build is scepter/focus specked for damage, and I use 30 Fire (V) (VIII) (XI), 30 Air (VI) (VII) (XI), and 10 Arcana (I) with Superior Runes of Rage and Zerker or Knight’s stats gear. It focuses on heavy crit damage, the use of the blast finishers that Scepter and focus have to grant might and fury. I generally use “Lightning Hammer,” “Arcane Shield,” and “Arcane Wave.” For my utilities, as Arcane Shield provides a little defense, Arcane wave is a good AoE to compensate for scepter’s single-target skills, and Lightning Hammer’s autoattack is a blast finisher (this is why I usually use the conjurer trait). The focus’s “Obisidian Flesh” an projectile reflection skills are your main defense, but this build really focuses on having someone to hold aggro for you. I’m not a PvP or WvWer, however, in my tests in PvP, the build generally does very well — its biggest weakness being hammer warriors who can spam stuns and knockdowns.
If you want survivability, I suggest using scepter/focus with 10 Fire (IV), 30 Water (III) (IX) (XI), and 30 Arcana (VI) (VII) (XI) with runes that improve toughness or vitality and either the Superior Sigil of Stamina or Energy, and the build focuses on using the focus’s defensive skills, plus a lot of evasion, and using cantrips to cure conditions and grant might to improve damage. You can also use the fire fields and blast finishers of the scepter/focus to grant yourself and your allies might.
I usually use scepter/focus, so I’m not very well versed in the interactions between scepter and dagger. There may be bette ways to create these builds by using scepter/dagger, and others may have better options regarding these builds.
Hope this helps