Is This Common For a Custom-Built Torque Converter???

The converter consists of much more than what you see outside. The weight includes everything within the converter, too. That is a small amount of weight to get one neutral balanced, everything considered. Look how thin those little weights are. There are normally two weights on a 360 converter about 1.25" long and roughly 1/4" or more thick. That is a lot of weight. Enough weight for an externally balanced engine, not what you see here. Just because it has weights (and a small amount, IMO) doesn't make it a bad thing. I certainly wouldn't condemn it for that alone. The next one you get may have weights as well. That simply means the converter WAS balanced.