If you have a volt meter, you can check the voltage at the battery terminals when the bike is rev'd up. At rest a good battery is 13.6 (or so) volts, when it is charging is should go up to 14 to 15 volts. If it goes up any higher, they your regulator is probably on the blink. Let us know what you find.
If you voltage tops out at 14 and doesn't keep going, then it would appear that your regulator is working fine and that was the best guess for blowing out lights by overvoltage. I can't imagine anything else that would blow the lights except cheap light bulbs and lots of vibs.
Unless your voltage regulator is intermittent and allowing the voltage to go to high once in a while - but that will be hard to detect!
The rectifier pack converts the alternating current from the alternator/generator to direct current. If one of the rectifiers were burnt out (open), it would mean less curent to the battery and your lights would probably glow dim. If one rectifer were shorted, the alternating current would get thru. You might check for alternating current at the battery (or light socket) -- there shouldn't be any. Let us know what you find .
There will be low voltage A/C off the rectifier. That is a Full Wave Rectifyer bridge and althought it is doide coupled, it does not filter off the residual A/C. The battery does that. It acts as a filter capacitor, if you loose a ground wire or have an intermittent groung connection,( near the battery) it wont filter the dc voltage ,,,, and your bike will be hard to start..... or....(near the regulator) the regulator no longer has a refference to control the circuit. Your grounds are just as important as any other circuit positive on the bike!!!!!!