I had a dull blade in a new pack of blades. Is this common?
The old rule of "you get what you pay for" definitely applies to double edge blades. I have often found that if a pack of blades is very low cost, the quality of those blades is probably not going to measure up to my standards.
Double edge blades are produced in countries all over the world. Some blades are manufactured in high-tech facilities with proven quality control (QC) measures in place, while other brands are not subject to the same level of craftsmanship. Although these blades are usually inexpensive, it is common to find inconsistency in the quality of the edges on them. It is unlikely that a new pack of razor blades will ever contain one that is too dull to cut hair during a shave, but in many cases the edges may not be completely smooth. Tiny metal burrs from the manufacturing process may remain along the blade's edge, which may leave your skin irritated due to the blade pulling on the hair (instead of slicing it) while shaving.
A rule of thumb is that the brands with reliable QC usually come from Japan, Germany, Greece, and Russia. While their blades cost more, you can expect consistency in the quality of the product. If you choose to opt for lower cost blades, it may be common to find dull or rough blades in a new pack from time to time. Learn more about blades in the article, Double Edge Razor Blades: Troubleshooting.