Warlords Mark doesn't give Mana leech anymore. You definitely need to find another way to leech mana. Life nodes as a Duelist are easy to come by, even for chaos damage related stuff. I'd also ignore the last Leech node in slayer for either Bane of Legends or Impact. Bane of Legends is always great and Impact will even work for Viper Strike and more attack range etc. I honestly dont know exactly how to build a Viper Strike oriented build, so I'm not going to make another mockup, but you can easily take up the Herbalism node for extra life and flask recovery rates and theoretically go towards the Revenge of the Hunted wheel to get more life with your current build.