I've seen more rusty E36's than E34's - although that said, I've not seen many rusty E36's either
Mate has an E36 323i, which is rusting around the windscreen fairly badly..
My white E34 has a bit of surface rust starting at the bottom corners of the back window, only seen when the boot is open, and not bad enough that it's an issue yet..
I guess it's all down to whether or not it's been in an accident & not repaired properly, BMW's just don't seem to rust, certainly not like other cars!
(I live on an island 9x5 miles, surrounded by sea - there's nowhere to escape the salt air here)