Considering there's new people running around with relic +1s and AF2, I think it's safe to move Legacy chars to new servers. The imbalance is vanishing.
This game has been out for a month. (A little more than, but with its issues, I think a month is fair to say.) If a person was max level their first week (unlikely but I'll continue) and somehow grinded their 300 myth marks each week, the most they could have is relic +1 and "a" piece of AF2. Lot different than if you're in the Legacy situation where you literally finished your character's optimization weeks ago and are just using mythology marks to contemplate the meaning of life at this point.