Haven't seen any threads on these and just read something interesting on the illusion / destro synergy thread.

Regarding destro staves only, what do they gain from the impact perk? What affects how much charge they use? Is this affected by -x% destro items? Do they add benefit to your other hand casting? Dual casting?

Can't test atm :'(

No gain from impact, you can't dual cast a staff the same way.

Amount of charge they use is governed by exactly the same things as how much magika you'd use by casting the same spell. What perks you have, what rank your destruction skill is.

Staves are a good fallback for midgame when you're struggling with manapool issues. At some point they become useless. Except for one particular artifact staff I can think of....

From the illusion / drstro thread:

"A destruction staff benefits from impact while allowing you to use only 1.0 magicka instead of 2.8 for the usual dual cast..
An spell in one hand and a staff in another = 2.0 dmg for 1.0 magicka + stagger = viable destruction after [level] 50"

Is this suggesting that having, for example, a staff of fireball in one hand and the fireball spell in the other will allow you to dual cast with the impact effect?