Don't assume my amount of alts hinders my skill on my main.
On topic, there should be a feat of strength I see no reason why not. It IS a lot of work to get all the way to 90 on every class - It's not worthy of a real achievement because obviously that would be unfair for people trying to get every one of them, but it definitely deserves a feat of strength and a title.
Why stop the achievement at 5 chars? It seems to make logical sense to have one for every char. Also, how are achievements like 'The Insane' any more deserving of a feat than all characters maxed?