Way of Dark
Ascension - Increase speed by 50% and receive 1/2 damage from all attacks. Lasts 15 seconds.
Cast Time: 1.5 seconds
Cooldown: 15 seconds
Ascension is an outstanding buff that not only augments your natural speed advantage, but is an invaluable defense boost as well. The down side is the long cast time. However, unless you get really unlucky, you should be able to find the solitude you need for this cast time. Always have a backup plan just in case. A melee-enhancing secondary ability or even your crossbow would be a good fit.
Leads to: Reaver or Dark Ranger