Like you pointed out, there are a few different bugs, but one of the things I'm seeing isn't really a bug, just an unfortunate feature I think.
I placate two Longbow, but because I don't time it just PERFECTLY one them fires and hits me, which takes me out of stealth, my Aura becomes unsuppressed, and the placate is ruined.
There should be a period of a few seconds after using Placate that a Stalker CANNOT be unstealthed by the same mobs that were just placated. It's just grossly unfair.