I agree he was off from his book characterization, but I feel like that might partially be due to him having such a comparatively small part (as does Hermione), plus the fact that they had to go OVER THE TOP with him in the beginning to contrast with Ron, husband of Padma.

That's a good point, maybe it seemed that a subtler difference would not make it clear enough what had changed. (Despite the playwright's repeated insistence that meddling with history had irrevocably altered the part in Ron's hair!!!)