While I still feel someone like Doug Jones would have been a better choice to play the character, Rupert Friend did a perfectly serviceable job, performance wise. It's just that the Grand Inquisitor's tall and slender physique is a key to his visual "alien" representation. Friend just looks like an average person in make-up, not an elongated species. George Lucas knew exactly why none other than Terrence Spence was cast as Tion Medon in ROTS.
Perhaps I'll buy this figure and see if I can scale down a Rebels Inquisitor headsculpt.