Touch of the Void is a horrible trinket. Sure, it has some decent damage, but the I feel like the trinket does more harm than good for a stealth class. The reason being, as long as those tenticles are attacking something, you will be in combat, therefore being unable to stealth for 20+ seconds isn't very useful.
Also defending champion doesn't heal you for 10%, rather increases your hp, and its an insignificant amount if you are at like 2.6k hp or whatever amount your glasscannon set is at. The reason AGM is good isn't because of the damage absorbed, but rather because of the ability to stealth while dotted. Also, once you use AGM, you can switch to vers trinket for 15 minutes.