We know too little about what spells are in and how they work to say dual wielding conjuration spells won't have any point. I can easily see a skeleton summoned by casting two of the same time (one in each hand at the same time) would not only make it more powerful, but last longer.
Indeed, I would assume that the original poster said that dual wielding conjuration spells would be pointless under the assumption that you couldn't have more than one summoned creature at any given time, but we don't know that. Maybe when dual wielding conjuration spells you can summon two creatures, one with each equipped spell, or combined the spells to summon a stronger version of the same creature, and I'm not sure how mysticism fits into this (Especially since mysticism doesn't exist any more.) or why alteration spells should be pointless when dual wielded.
I'd say that we really don't know enough about the dual wielding mechanics for spells to judge them, but in any case, if you want to play a battle mage, then you should just wield a sword in one hand, and a spell in another, which of course means you can't dual wield spells or use a shield, making a concequence to choosing that approach. Now, I'm not sure if I necessarily like that or not, because I liked being able to cast spells without putting your weapon away in Oblivion, but that was partially because Morrowind's system required you to awkwardly switch between having your weapon drawn and entering a "casting stance", whereas the new approach sounds a little less awkward and more tactical, but that aside, saying dual wielding spells could be "useless" seems to mostly be an assumption made based on how spells worked in Oblivion, and how they work may have changed in Skyrim, so we can't rightly make such a statement until we know more about how magic works in Skyrim.
Well, if you first cast 100% elemental weakness spells on the target Apotheosis could dish out a hefty 200 damage in one strike. Two Apotheosis' would a) negate the need to cast the weakness spells for ridiculous amounts of ranged damage and b ) would make 400 damage if you were toting around elemental weakness spells. You could blow away Minotaur Lords with that kind of firepower :gun: :shocking:
As for the class I suppose it wouldn't matter. Dual-wielded staves in general sound like a lot of ranged damage. Not that I won't enjoy abusing this . . .
But we don't even know if such a powerful staff will exist in Skyrim.