Oh that's true. When I was watching it I wondered why he didn't vary the serve, its effective because of power but against the top 4 they would be able to read that serve better than Grigor did today.
Taking only the top 4 into account, it's not a big issue against Federer and Nadal. Against Djokovic and Murray though, as soon as they read his patterns he stops getting free points on serve. Actually, even Ferrer can read his patterns like an open book, hence JMDP's struggles against him.
This is definitely something that can and should be worked, he has improved his serve a lot in the last year but it's still too predictable and a liability against the best returners.