Ah come on now, Never say impossible!!
Yes, I always found the end to be the hardest, sometimes the bosses can be a little bit harsh.
If you still haven't dont it by tonight, I'll probably be online around 7PM GMT, add me (Hitomi Kyoko) to friends and I'll give you a hand. By the by, I'm feeling so helpful because so many people helped me get "Protector of Cantha" last night - people should be more helpful like last night!!
Edit: As for tips, I can't really suggest anything other than just to find a group to steamroller through everything. I always go the top way, past the waterfall, I don't know what the caves are like. Maybe a good idea to take a ritualist with protection spirits to cast them at the end of the bridge to help protect people fighting the bosses.