Alexander Siddig was confused, surprised and a little dissatisfacted apparently

[Chilli]

But the show did a very good thing with Pedro Pascal/Oberyn. I never cared for Oberyn in the books but he was absolutely my favorite character on the show. A pity he had to die.

Alexander Siddig was a good casting choice too, but I think it was too difficult with the limitations a tv-show has to really explore his character. In a book, you can write as many pages as you want and you can spend as much time in (re)writing as you want to make it really what you want. But a tv show has limited time and money to do all these things and it's difficult to correct filming/script mistakes/weaknesses in the editing room.