Hmm... I'm seeing way too many abilities keyed off of PI points with far too few uses, though Paragon of Thought may help with this. 1/2LvL+Int for an entire day when you can spend up to your level blocking an attack seems... lopsided, I guess? Do you intend for PI to be Per Encounter, rather than Per Day? That so many features use PI and so much can be spent to that end seems to suggest it.
My first impression gives me a sort of Incarnum Sorcerer feel, which may change wildly depending on actual Circles and Concepts. When I say Incarnum Sorcerer, I refer to how your focus can change wildly from day to day. Though that leads me to thinking about how it might be nice to have the ability to slightly modify your focus during the course of the day, but depending on the Circles and Concepts that might be silly.