The discogs import correctly removes the denotation for multiple artists with that name (such as 2 in parenthesis) when it is located at the end of the artist import string. However, it does not when it is after.
See for example of such: http://www.discogs.com/Arty-2-Mat-Zo-Rebound/release/2870583
Thanks for the report, is now fixed in git.
Fixed in version 2.0.