Me neither, haven't tried it that many times but four player Osgiliath seems close to impossible. I had though the same about it solo when it first came out but with the current line-up, Beravor (even after the shaft), Elrond and Glorfindel (Spirit) I can finally say I am confident of beating it much more often than losing it.
I think the Lake Town challenge might be very different, surely something new and it may take time to realize a good strategy against it. When Osgiliath was first previewed, people were also screaming though.
