Fire/Poison Mage Builds Post-Big Bang?

Seems like an all around nice build, except in 4th job I would max infinity before bigbang. From lvl 1-30 bigbang doesn't get that much stronger (232% to 290%) while infinity gives a nice boost to your range every 4 seconds.

Does infinity increase by the base magic atk, or is potsmart for something like Swiss Cheese cuz that would be amazing.
And which skill contributes to better dps for bossing, Fire Demon or Meteor?

Fire demon increases your dps more than meteor.

Infinity is quite a good increase to your average damage but because it is a rollercoaster you can't rely so much on it for training.