Seeing how you cannot buy Shadow of Mordor without it being the GotY edition, which costs $5 - or $10.50 if you buy the bundle for both games, this DLC is just free bonus content for you to enjoy.
This DLC's bonus content is focused on Torvin and the beasties of Mordor. Talion and Torvin have an interesting chemistry together where they're bouncing off each other with slights - Torvin leaning into the Talion's old job and Talion leaning into the fact that Torvin is vertically challenged. You might imagine that it would get old fairly quickly, but honestly, I found myself enjoying it quite a lot.
That aside, there are unique Warchiefs up for interesting fights, like one that straight up RIDES A GRAUG, so there is quite the interesting bunch of gameplay mechanics that makes this DLC enjoyable. It isn't long but if you're reading this, wondering if you should buy these games, you certainly should; and you can't avoid getting this DLC along with the rest of the game. I recommend playing this DLC after you beat the main story and before moving onto Shadow of War.
An interesting note: Celebrimbor has no voice lines (besides the usual ones when you dominate an Uruk). I guess this is to balance out that he has his own DLC without Talion. It isn't a problem.