Fire/Poison Mage Builds Post-Big Bang?

1st job
1 Bolt
Max Magic Claw
Max Magic Armor
Max Magic Guard

2nd job
1 Teleport
1 Fire Arrow
Max Mastery
Max Fire Arrow
Max Teleport
3 MP Eater
Max Meditation
Max MP Eater
Max Slow
1 Poison Breath

3rd job
1 Teleport Mastery
1 Explosion
3 Elemental Amplification
6 Booster
Max Elemental Amplification
Max Poison Mist
Max Teleport Mastery
Max Explosion
Max Elemental Composition
Max Elemental Reset
Max Partial Resistance
11 Seal

4th job

1 Paralyze, 1 Meteor, 1 Big Bang
Max Buff Mastery
Max Paralyze
Max Big Bang
Max Infinity
anything but Mana Reflection

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?