I tend to agree with you, we have little information that seems to imply Asmo is great at anything the Shadow deems important. Yet, he lived into the next age when all but 12 others did not. Based on what RJ has said, the followers of the DO schemed and plotted against each other at least as much as they did against LTT et al. Asmodean survived that as well to be important enough to be summoned with the other 12.