When should I start training at Oblivion 4?

Not really, the map sucks, the exp:hp ratio sucks, and they do more dmg, and have 3 different attacks.
I see no reason for it to be better unless you are an F/P Mage...
Edit: AND they are weak to fire, neutral to everything but poiso...zzzz.... I say they suck

I thought we were just talking about Buccaneers here but Oblivion 2 is definitely better than Skeles for ranged classes. I train about 10% faster there.