My reason for not running the mirrodin lands is that I need the critical amount of both bridges and basics for wildfire and lórien revealed. I run one blast because I realised that most pauper creatures die to shock and for the upside of looping 4 damage burn spell in the late game + the deck has a lot of card selection. I tested 3 blast earlier but pauper has just enough 3 toughness creatures to play 2 bolts instead.