Virulent Shot is a % based proc (65%) based on the skill scattershot. The idea is to get scattershot to crit. Scattershot is a ranged direct damage ability so it works perfectly with sets such as Eagle-eye or Wrath of the Imperium but also works great with agility. Max range for this is important because It will tick 6 times over 12 seconds at distance which translates to a 30-45k proc (crit). 65% of the damage that scattershot hits the target for times 6.
As with all my bow/bow builds I used Bosmer here.. since they are the best :) You shouldn't need to use the trial dummies synergy for resource regen with any of my builds. Bosmer stamina is pretty great. There is a back slot open for whatever. The build is super flexible though and I really encourage you to experiment with all my builds.