Shadow of Mordor GOTY Upgrade: Is it worth?

It introduces two shorter campaigns that are still quite good. It's more of the same, but if you liked the original, you'll like the two campaign DLCs, so yes, I would say it's worth it.

I woudn't say it's worth it. Although the campaign with the dwarf is quite enjoyable, I cannot say the same about the elf campaign (interesting story but I personally found the gameplay tedious, I am not sure why). I'd say if the price of the upgrade is small andd you loved the main game and would like to try some new moves/mechanics then go for it. Leave it if you would miss the moniez or could spend them for something else.

Well, the DLC don't offer anything new. Save your money and just play the vanilla game.
Or buy Mountain.