a) identical tags (except name which is not important) - throw away the copy/copies. I think here it is clear the copies are not needed.

b) identical tags (except name) plus more tags. 

Eg way 1 has: key1=a key2=b     way 2 has key1=a, key2=b key3=c. So throw away way1. 

If there is however 

way 1 has: key1=a key2=b  key3=c    way 2 has key1=a, key2=b key4=d. it is more complicated but it could still be merged to a single way consisting of key1=a, key2=b, key3=c, key4=d

if 

way 1 has: key1=a key2=b  key3=c    way 2 has key1=a, key2=b key3=d we could keep both ways, or throw away one of them - but yeah then it is not clear which one so better keep.

For the problems related to  http://www.openstreetmap.org/browse/way/310376420 

and the other 2 ways. Following a) removes one copy. Following rule b) would actually get rid of the second copy and now information/detail will be lost.

I'll try the new patch and see if I can find out more about problems.

BTW - would it not be better to just use a test map for finding the error? I'm pretty sure any 6 routable roads on top of each other (identical direction) cause routing to break on Oregon 600. As soon as some way is slightly different angle - it is fine.