Obviously with this during x2 it was fairly popular but now it seems it has died out.
What would make the caster version worth the time to do at least as a daily since we get the talisman quest once a day?
I think something as simple as the "first time" quest we got being a part of the daily would make this a strong option for many with a gauranteed drop to keep.
Adding the extra bosses that a "normal" Nirvana gets might help also adding the extra chances for drops.
I do realize that the caster nirvana's are comprised of a lot lesser geared players and that for many Clerics and Venos it is easier to just do "regular" runs. I have done a lot of runs and have only completely failed once. Many of the runs I did, did not have high refined weapons and a majority of them still went smoothly as long as everyone knew what to do (or for caster nirvana's -what not to do-).