Sharapova's problem isn't consistency...it's lack of weapons. Unless she fixes that serve, she isn't beating the elite and is mightily suspectible to even lower-ranked players having a good day.
Her serve is a letdown for sure, but she doesn't lack weapons. She still dominates off the ground. She lacks consistency.
The thing is that this board has a different understanding of the term 'consistent' as I and probably a few others do. When I think 'consistent' I think of level maintained throughout a match, and throughout the tournament, not results (so I'm actually with Caro fans when they say that she's more consistent than Kvitova, but that's not really the discussion here but I'm just saying (I like Kvitova and dislike Wozniacki btw)).
Maria has had consistent results, yes, but she doesn't have the consistency in her game. We've seen it multiple times this year, cruising through some opponents in Miami and then struggling majorly against a weaponless player (Dulgheru). At Roland Garros, she had a few good matches, but was dire against Caroline Garcia and Li Na. At Wimbledon, she struggled against Robson, played pretty badly against Lisicki. At Cincinnati, she did ok-ish in the first few matches, and then the final was just a horrorfest.
Unlike the old times, this year she was unable to string together more than 2-3 good matches in a row, before having to dig deep and scrape through another opponent she should beat comfortably.
THAT is her problem.