Problem has been solved:
While the tensioner pulley does seem as though it is due for replacement soon, it was NOT the cause of this issue.
I was going to mention the "far fetched" idea earlier that there could possibly be something on the belt, causing tension to build and release every time it goes over a pulley. But I figured people would think I was crazy.
Well, that turned out to be the problem. The cause was a sh*tty Continental belt from PelicanParts.com. I looked at it after I got it off and you can see buildup on the grooves from the manufacturing process.
Went around the corned to Advance Auto for a new one and low and behold; no more horrendous sound.