Here is my life steal build,
http://en.gw2skills.net/editor/?fQEQNBIhZakRrSPTTZjePBMpwbujeg8yMTpYd2B;T0Ag0CnosyYlwKrVOrkWt+YYxBjXFzRA, use Omnomberry pie for 66% chance of 350 life steal x 2 = 700 cause you benefit from your bloodthirst (Siphoning health is 50% more effective). It is a 1 sec cooldown, your sigil of blood heals you for 450 each (33% on a critical) it is a 2sec cooldown. You can also put two sigils of blood instead of one and an accuracy one. Your vampiric traits gives you around 120 hp sec. So basically if you attack a person with 2 sigils of blood and an Omnomberry pie, you do around 1000hp/sec.