I am just now trying out the mage class and am considering making a pure fire mage, what I want to know is, what are the benifits and deficits of this? Would this build be weak in comparison to combo builds such as arc/fire or frost/fire? what creatures or areas would I need to avoid with this build due to immunity to fire damage?

Your final choice in talents needs to be based on your playstyle. With TBC there are now more talent setups than before so there is on 'cookie cutter' build for fire-frost or arcane. Let me give you a brief overview:

Fire is generally about damage.
Frost is about survivability.
Arcane enhances both.

You can now PvP as both a Frost and Fire mage, but PvP talents tend to vary a bit from PvE talents. (Too long to discuss here, but PvP is about, survivability, crowd control and burst damage, PvE is about sustained mana efficient DPS.)

PvE builds tend to be a blend of Arcane-fire or Arcane-frost.
PvP builds tend to be Fire-Frost heavy (41 talents or so) and rest in Arcane or an Elementalist build... Fire-Frost only.

Thats about it to start. Check out the mage forums and play with the talent calculators a lot before changing. It gets real expensive if you put the wrong point somewhere.

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