I went back and played around with some of the boss fights, and about 80% of the attacks used by bosses do not engage with the blocking mechanic at all. Doesn't help you in Magnet Met or Tornado Met's boss fights, the only thing you can really do is dodge.
Also it seems like most of the shield-focused mechanics were saved for the Wilet stages, which... one of them is just 3 reflecting light lazer puzzles which are always lame.
Yeah, I felt the reflectable laser puzzles kind of broke the pacing of that one level. Of course, that's the sort of issue you can potentially run into if you do dedicated puzzles to get something out of a mechanic.
Also, can I just say, I wish you'd be able to turn off the sound effect for your guard meter recharging. It's distractingly loud (as are many other sound effects, like the ice storm in Ice Met's stage, I turned sound effects down to 20% because of that).