If the tank is lower than the sink, then yes, the faucet may need to be left on. Alternately, you can unscrew the hose from the tap once it's full and place the end in the bathtub to let it drain. There are switches on either end of the hose, so you can fill the hose with water, turn the switches to seal it shut, move the non-tank end to somewhere low, and start it up again. Slightly more work, but still easier than bucket hauling.
If your tank (or at least the section of the tank that you want to drain) is higher than your faucet, you're good.