If they want to bump up warrior dual wield a little, maybe they might consider giving us an innate haste boost when we dual wield that stacks with everything. Possible? I don't know.
Monks and Rogues have proc AA's that grant 'HundredHandsEffect' which does something similar (Fists of Steel and Etherium Blades) I'd welcome something like this for Dual Wielding Warriors.
What about something that would increase warrior group desirability. Instead of a personal dps increase, what if warriors duel wielding could proc a very short ac debuff (1 tick)? It would make melee want to have warrior tanks. As well, the short duration ensures warriors don't proc and then switch back to their shield.
Tricky. It would have to be fairly potent to be more worthwhile than a personal DPS increase. You'd see more impact on raids with stacked warriors/melee. Opposite direction we want to go IMO.
Whatever it is, it cannot be to large of a dps increase, as tanks shouldn't be doing damage near dps classes. Thats why I was thinking of a utility or adps effect, you get more out of it than a 100dps increase.
Considering DW is behind our 1h damage and our 1h damage is quite safely behind DPS classes, I think we've got plenty of room for significant DW boosts. Certainly plenty of ways to do this, but this thread's scope was attack speed, where I think HHE applies best.