Under the right defensive setup he is fantastic, we saw it with Pep and we're starting to see it again with Tata. He isn't the type of defender to give you match winning performances in spite of a shit defensive setup, like a Puyol or Vidic for example, and I think that is why he was frustrating to a lot of people over the 2 seasons.
The fact is we haven't been that good defensively in that time and because Pique is very system dependent it seems, he stuck out like a sore thumb while we were expecting him to step into the Puyol role, he can grow into that with time hopefully.