Note: I meant perk not spell >.<

Im pondering wheter to take this perk or not. I plan to powerlevel up conjuration to 100 and I use bound weapons for soultrap.

Since thralls are permanent, is taking the dual cast conju spell worthless for me? Is the duration really the only reward for taking this perk?

There's not much of a point taking it ever, sadly, since it's considerably cheaper to just resummon it every time it wears off than to DC it. It's like that with every spell college: efficiency goes right out the window when you DC.

Edit: Just realized I didn't specifically answer your question, sorry about that. Yes, duration is the only thing DCing increases for conjuration.

Except that for Illusion, without DC, you cant frenzy things past level 40 without it - for example.

Thralls are just as useless as is dualcasting conjuration (except for death thrall maybe, doesn't fit my char).

I wonder, you can only Thrall the Storm Atronach btu I think he isn't leveled. You can't Thrall the Dremora Lord. Is that true? So, as you said, the only point for permanent summons are resurrecting some bosses, if possible, like some named Bandit or Draugr. The Strom Atronach gets killed fast at higher lveles I presume?

I'm not that high level, just 38 now but the 120sec for Storm atronarch have always been enough. He either gets killed before time runs out or i just recast him. Thrall just tend to block doors without an option to just wait until they disappear at the cost of even more magicka.

And i don't use the dremora lord, doesn't fit my char.

Dual casting is completely worthless for master level spells in general, they are casted by both hands anyway

Dual casting may be useful only for the destruction and illusion schools of magic.

It is only useful on the raise dead spells

I agree with dual casting being primarily useful on illusion and destruction spells. However, I want to throw on restoration. It's nice to fill up my HP bar with Close Wounds in one cast.