Was he a below average puncher or was his lack of aggression the reason for the modest number of KOs?
More his technique. He had decent hand speed, just threw more 'arm punches' then sitting down on them.
McCline hit pretty hard when he threw with intention. He dropped Briggs (bulked version of him), Brock, Byrd, Peter (3 times), Al Cole among others. All the aforementioned guys had sturdy chins. But McCline often took a safety-first approach, and lacked that killer instinct when he had his opponent hurt.
Decent. With back-to-back-back wins against Grant, Mount Whitaker, and Shannon Briggs, he put himself in the mix. However, I feel guys like Kirk Johnson and Larry Donald would have pummeled him, and Ray Mercer, David Tua and Ike Ibeabuchi would have shut him down, and quickly.