In PvE, you need to use a staff.
The spell damage from dual-wield and the 129 from Torug's Pact is not going to come anywhere close to making up for what you lose by not using a staff.
What the staff gives you is the weave. A free light or medium attack with every cast of Funnel. Even if you do nothing else, just weaving will get you more DPS than straight-Funneling from your DW bar.
But that weave gets you so much more. It procs Assassin's Will. Even with expending one GCD to recast Merciless after firing your spectral bow, it's still worth it because it hits harder than two Funnels--I've seen my Assassin's Will hit for as much as 46K. And you do have to keep Merciless up anyway for that 8% damage buff. If you're on PC, the Srendarr addon will helpfully sound a ping every time it your Assassin's Will procs, which makes it much easier to use.
Weaving builds ultimate.
If you have Siphoning Attacks up, it means that every weave will proc a guaranteed SA return of both magicka and stamina.
And there is one staff ability that you should use: Elemental Blockade. With the buff it received in TG, it's now one of the best DoT abilities in the game.
Anyway, the standard magblade front bar is a staff with the following: Funnel, Crippling Grasp, Blockade, Merciless Resolve, Inner Light. You can leave Impale and Sap on your dual-wield bar since you don't weave those.
@aLi3nZWhat does suck is losing a set bonus like 126 extra spell damage set bonus you get from 2x tourges pact swords.