Might I guess that you are avid gamer or was one before? Since I had exactly same feeling when I read Mistborn and didn't find agreement on it with some people who are far more into books rather than games. Though I didn't have same problem with any other books probably because they have less action scenes.

All his magic systems have well defined mechanics and strict rules behind them so it's kind a expected and I feel like somebody who used to play a lot of games see through it more easily. Whatever it's good or bad depend on your own preferences in fantasy.

Personally I see this as a good thing since opposite would be ever repeating contrived coincidence of just-one-another arcane trick rediscovery. Probably these limits on what magic can or cannot do is one of things that make him improve his writing.