Small fluctuations can cause continuous artifacts in rare cases.
.01v fluctuation is bad. (Even if the voltage stays within tolerance) The regulators on a modern day video card / motherboard are supposed to be stable within thousandths of a volt (.001) Thats what the feedback (or error) loop is for. (the area you are drawing on with a pencil) It precisely detects the GPU voltage and varies the duty cycle on the PWM P/S in realtime. In theory, there should be NO fluctuations, even under load. (My voltmodded 9800 pro at 1.9v has a fluctuation between 1.9001 and 1.9004, I thought that was bad enough.
If your card fluctuates without a voltmod, you have an overclocking lemon and shouldn't voltmod it. (unless you know how to change the regulator chip and mosfets, and can find replacements) Fluctuations of that magnitude means your card has a not-so-good VR chip, or an out-of-spec resistor or coupling capacitor. It's also possible that graphite powders from the pencil ended up where they shouldn't be (under resistors, between chip leads, etc.
You can choose to believe me or not seeing as I'm not an ATI Engineer (I've had over 15 years of experience with digital and analog electronics and specialize in power regulation circuitry) What I know is 10% textbook and 90% practical real-world experience.
My only recommendation is be real careful what you do to that particular card.
(and keep an eye (finger) on the Regulator chip. If it gets hot or even warm, you got a problem.
Ask ViperJohn about this one, more than likely you will get the same response. (Seems he might know even more than I do about Radeons specifically)
Remember, smoke is very important, once it leave the chips, you cant get it back in. lol