Yet, somehow they run and cast as fast as players with 50 ping. I don't call that bravery, but hax.
If you have a ping around 300 ( in CMD line,not in game) but have no obivous packet loss,you still can run fluently.Ping plays a significant role in spell casting.No one with 250+ ping could cast as fast as players with 50 ping unless some new exploit like 'target exploit' appears again.
Playing a dexxer or an archer under a high but steady ping wont give you too much sense of frustration.However,if u want to play a mage effectively,especially if u dont want to be a 'Support' but 'APC',Ok,Good luck.
The saddest thing about this game is that ping affects and limits your gameplay too much.