I have seen it cross 5 seconds. If you need it in a pinch, you'll die. In a less dramatic scenario you or the other healer will likely just cast something else, because the other healer doesn't know if it's coming and you may not know if it already went off.
Suggestion: make it into a shield (that can stack with every other shield, please).
Also it needs to share a button but not a cooldown with Consolation, the second charge of which is unwieldy with Seraph's duration anyway.
The faerie is just a mess.