Random augments aren't going to make Relic gear outshine Emp gear. Emp gear is just too perfectly suited to each job with amazing stats on every piece. At best you'll just be using the same situational pieces as before only with a few extra random stats added.
Personally I'd rather just have fixed stats with those situational pieces made into better situational pieces e.g. Assassin's Armlets with Treasure Hunter +2.
Synergy is garbage and has always been garbage. SE isn't going to make it any less unpopular than it is now by trying to ram it down our throats. Abjuration gear augments didn't change this and Artifact gear augments won't either. If it's based on Synergy people simply won't bother.