I read the ritual that Odren gives me and then i speak to Demogorgon and agree to his plan. I talk to the Helmites andthe to the Ghostly apparition. I agree to use the new scroll to seal Demogorgon and Odren inside. The i get the message that the party has recieved an item but it's not in my backpack or anyone elses! No one's backpack is full btw, and it's not on the ground, i've triple checked.

Am i missing something?

Yes this sounds like a bug, you could either:

a.) use CLUAConsole to give yourself the scroll
b.) revert to the nearest save and try again
c.) wipe the floor with demogorgon and forget the scroll!!

i kinda fixed it... I just said i'll go kill Demogorgon and she gave me the scroll.

ANyway, i thought this guy was supposed to be tough. I'm not bragging or anything but he didn't last more than 4 seconds.

I just used improved whirlwind on Minsc, Korgan and Sarevok and cast simultaneously 2 Implosions and he died.

I didn't get to even see the tag that says "Near Death". Hmmm...

Indeed, demogorgon is a complete joke in an unmodded game. A solo fighter on insane difficulty even has a ridiculously easy time. In fact, my opinion is that the final guardians are much harder than demogorgon himself!!!

You should download the Improved Demogorgon...he becomes much more difficult to say the least!

Yes, the guardians were a little tougher then he was, but not by much...

nataben knows what he's talking about, I've downloaded those files as well and it does make Demogorgon (and Illasera, Yaga Shura, ...) more challenging.

http://www.sorcerers.net/Games/BG2/index_mods_hosted_bioware.php
They're all official files, as you can see here.
Throne Of Bhaal Enhancements From BioWare's Senior Designer David Gaider

Not technically official - they aren't supported by Bioware, as Mr. Gaider is very careful to point out. But yes, apparently Demogorgon was dumbed down quite a bit because it was feared he wouldn't be defeatable by most of the playerbase. (Duh. He's Demogorgon.)