OTRS version 2.0.4 should be immediately updated to 2.0.5 (stable) due to multiple security fixes. OTRS versions 2.1.6 and 2.1.7 have both been released. Latest ~arch is 2.1.5. 2.2.0 should be here in about 4 days. Current 2.0.x ebuild *does* work when tested against otrs-2.0.5 locally, and 2.1.7 works on 2.1.5 ebuild.
*** This bug has been marked as a duplicate of bug 177630 ***