EP's suggestions look good to me.
My ads are that once the garrot is in place:
1) The strangler would grant CA to anyone not the target.
2) The rules for "suffocation during combat" on pg. 159 of the
DMG would apply (this would be in addition to the 1d6 damage sustained each round from the garrott itself).
Frankly it's sort of a slow way to kill someone who has a decent number of healing surges. I wouldn't try it during normal combat unless I had a Bugbear Strangler-like ability to use the target as a meatshield. I guess it's a good option though if the target is alone and you need to take them out quietly.