Another (probably better in your case) approach is to reshape the data before feeding it to Tableau. Tableau works best with normalized data.
Preprocess it to look like:
Name, Score, Tag
Joe, 5, A
Joe, 5, B
Phil, 7, D
Quinn, 9, A
Quinn, 9, C
Bill, 3, A
Bill, 3, B
Bill, 3, C
At that point, the standard Tableau word cloud charts should work well, and it will scale easily as you add more tags and data.
Reshaping data to normalize it prior to analysis with Tableau is a pretty standard step. Sometimes you can do it automatically, say with custom SQL, but often you'll have to use some sort of script first. If your data comes from Excel, Tableau has a plug in that can help with reshaping data. Look for it on the Tableau knowledge base.