I have a few questions that I have not been able to figure out on my own.

First- If I drop phase walk will my healing companion benefit from the bonus if he is standing in the pool?

Second- How can I get shot with some kind of tranquilizer from a imp if I am stealthed? I guess he had me targeted before I cloaked, but why can he still shoot me?

Third- If I am attacked by a player while fighting pve and try to force cloak, I almost always break cloak before I can get away. What is happening that makes me break cloak?

First : I'm not sure, but look at his buff bar

Second : Some talents improve passive stealth detection, it's possible he simply saw you.

Third : Typically, taking damage. If the other player or an npc put one or more DoT on you, you must remove them before going into stealth.