Why is Hashim Amla so tough for indian bowlers to dismiss?

He isn't the best batsman in SA side, leave alone in the world but weak Indian bowlers are making him so good but then again, every team has a successful batsman, who does better than others, in most of the matches, played in a bilateral series, Amla is proving to be that batsman, in this series, must be wishing, for a 5 test series, with such good scores, in a short 2 match series.