It wasn't yet. Garithos even sent the Blood Elves on a suicide charge against Dalvengyr's meat grinder and the other passive undeads at the site would've been brought to his side or the other dreadlords when Illidan completely removed the Lich King's control over them.
Orgrimm turned away the Alteraci seeking for refuge and protection after they got sacked by the Alliance of Lordaeron. There's a reason why the Syndicate hates the Horde too