Actually, I've used troll alot (one year out of the one and a half that i have been playin). I made a build that helps me alot most of the time. I use Maelstrom/Mjollnir with vlads
the only way this can stack is if you equip mjol while in ranged mode (getting the ranged version) then putting on vlads in melee mode. this makes it so that when troll attacks, he gets lifesteal except when Chain Lightning procs.
I have not seen CL not proc on any attack. it even procs on autoattack this way.
not sure about the mechanics part (even though this is the mech forum) but im saying all this just from experience.
hope it helps