I have to admit, I found it very disappointing. Primordus was like the end game boss and you end up killing him in a living story pretty much. I thought killing Kralk in a living story episode was uninspired, but Jormag and Primordus in the same time is just shockingly uninspired and an awful choice.
Primordus was pretty much the emblem of the game and everyone was scared of him waking up, only to have him and Jormag kill each other in a 10 minute instance.
It's just... disappointing, I would have thought Primordus deserves an expansion of his own, not a measly 10 minutes.