I ran this tonight at the low tier. I was initially supposed to have six players but one dropped out due to technical difficulties. I had a level 12 barbarian, life oracle, magus/lore warden and paladin/cavalier along with a level 13 wizard.
The whole thing took a little over 5 hours to complete once we factored out breaks. This was largely made up of difficulties with the first encounter.
This fight on its own took about two hours to complete. For most of the battle none of the PC's were able to reduce their miss chance and that played a huge role in the fight. I did manage to abduct one PC after about 5 rounds of trying which unfortunately was the lance using cavalier who became effectively useless off his mount stuck in the astral. He did kill the shamble that brought him there so at least he didn't die.
As others have mentioned having a situation where you need someone abducted to get the next breadcrumb in the trail is a bad idea, at least unless there is also some other way of finding he same information. It is very easy to miss as the chance of anyone being abducted is quite low.
I did nearly feeblemind one of our local VC's but he saved after misfortuning into a 1 then using his shirt reroll. Thinking back on it the rerolls should have also been affected by persistent.
When I played the fighter got petrified. When I ran it tonight she got possessed. I triggered the wishbod on possession although it is unclear to me still if I should have.
I did quite like the addition of the extra prep stuff for them although the fighters benefits could have been rather more substantial with little real risk. The limit to the conditions she can gain save bonuses to was too narrow for a high tier adventure. Honestly you could give her all three benefits and it wouldn't make much difference.
If I had one concern about the fight it would be the nature of the four player adjustment. It removes a pre cast buff which might not well have any relevance at all and she doesn't use one of her more minor class abilities. I do think a group of four would really struggle, if I had been running with one fewer player I strongly suspect the end fight would have been a TPK.