You need to be running the lists through multiple data vendors, not relying on one. AND regardless of what you do some markets are just harder to "reach". No amount of data and scoring will change that.
Example: If you are targeting logistics the reach will be super high. Meaning if I target a list of 1000 people I can easily reach 250-300 by the phone. If I am targeting CISO/CTO I will reach about 100-150 of those people on the same list of 1000.