When the dot blinks in a regular pattern, that is a low battery. We alway recommend installing a new, high quality (no dollar store stuff) batteries before a match. If you want to be 100 % sure, check the battery on a voltmeter. A new battery should be 3.2-3.3 volts. Often old or dollar store batteries will be 3 or less volts right out of the package. The dots will experience low voltage issues around 2.8 volts.
When we offered a competition orientated red dot for the market, dot brightness was one of our biggest priorities. Lots of dots were too dim to use under the bright sun. This does mean the optic will tax the battery heavily but that is a small price to pay for the benefits.
Considering what a match costs you (travel, ammo, gas etc), a couple of bucks on a new battery is a MUST!