One of the three wires from the stator acts as a trigger for the headlight relay, so if that wire isn't getting voltage, you have no headlight (unless you do the blue-wire mod). Or your relay has burned out.
Doing the blue-wire mod doesn't really re-route the circuit so that it uses any NEW components that might be causing a vampiric drain. It's more likely that your stator and battery are limping along just barely keeping you on the road when your headlight is off, but when the headlight is on, you're drawing more amps than you're producing, and you eventually run out of pixies.
11.5 is more than "lower than it should". It's "failing horribly".
I recommend you yank the 10-pin connector out of the junction box, remove the yellow wire, then plug the connector back in. Start the bike and check for AC voltage between the yellow wire and the bike frame. Don't let that wire touch anything while the bike is running! If you don't read something like 5v AC (don't know the "good" range) there at idle, your stator is fried.