Basically, I found that users upload artworks from the same artist using different artist tags:
shogun_(a96040021);
shougun_(chuckni1);
chuckni1;

I myself not an active editor but decided that's something I can help with and I miserably failed this task. My idea was to specify that all 3 tags are aliases to one but that just didn't work.

Was the correct way to delete two of these artist tags, update artworks with remaining artist tag and then add aliases to it?

Submit your request to forum #22465 thread and post some more info about artists in question. Wait a week or two, and if nothing is done, PM mod with your request, or if you're sure you are totally right, retag yourself. Mistakes happen. Select the latest artist's nickname he's currently using and retag with it.