OchreJelly
First Post
I shall research this. Is there a charm ritual that can be subtley and quickly cast upon an individual that doesn't involve the victim having to be bludgeoned down to 0 hp to work?
You probably won't find such a ritual, but that's a feature, not a bug. What it sounds like you're arguing for is basically a save-or-die effect, which the 4E designers made great efforts to avoid.
That said, is such subtle charm magic flavorful and iconic? Absolutely. Does it have a place in the game? Maybe, but it doesn't have a good fit in the current system.
Some people have found creative use of encounter and utility powers outside of combat. For example, it's possible your DM could allow you to make creative use of the bard's "fast friends" power outside of combat for the spying scenario, but that's really a stretch on the power's utility.
It's better if the solutions could be worked into a skill challenge to avoid the SOD problem. Maybe work up a challenge where the RP encounter starts with a charm like "fast friends" to disorientate the npc, then allow for bluff checks to continue the diversion, while arcana checks are used to "up the wammy" of the charm effect until the NPC becomes your trusted friend.
It has the feel of subtly and trickery you want and if the challenge fails, the NPC is wise to the trick!