The international market is a roll of the dice in a lot of ways as you have pointed out. It's difficult enough to judge a prospective stateside draft candidate at age 17 or 18 and it almost gets to be geometrically different when a scout is looking at 15- and 16-year-olds in the international realm. Differing rates of physcial maturity simply mask where a kid will truly end up. My guess with Maitan is that he was ahead of his cohort in terms of physical development and that when the rest of the cohort caught up physically, he was no longer that special. He's not that rare of a case when you look at highly-publicized international signings who didn't perform up to expectations, but the fact that he was at the center of the sanctions and he didn't get above AA puts him in the spotlight to a greater degree.
Looking back I feel Andy Marte was the same way.