Frost versus Fire: two talent trees that the new World of Warcraft mage can choose, but only one they will be able to master. Fire gives much more damage, but Frost grants the added ability of slowing down or even freezing afflicted targets.

For any spell caster's choice against angry mobs and traitorous players, they would choose the obvious tree that should give them a few more seconds of survival. The Frost tree provides that option. Shields, slowing down or just freezing enemies, and summoning minions under the ice element all provide a reasonable chance of escape for a mage.

Aside from the critical bonuses added to spell damage, the talents under the Frost tree even allow you to completely destroy enemies by shattering them while frozen. It was a pretty great talent tree, until Blizzard thought some spells in it were unfair. The resulting changes made the Frost mage unable to inflict critical damage and freezing effects all at once.

By default, all ice-enchanted attacks freeze targets (unless they were freeze-resistant) and continue to persist as frozen until the freeze time counter expires. But if critical damage is dealt, then the freezing effects are negated and the target resumes it's normal condition.

The idea behind nerfing the freezing ability was due to Frost mages being able to continuously inflict critical damage while targets were completely helpless in their frozen state. They refer to this as "chain-critting." But like some issues, the justification for the downgrade isn't all that...well, justified.

Blizzard may have identified that the "chain-critting" feat could be potentially evil to the gameplay balance, but they haven't really reviewed the whole picture here. Armors exist that resist freezing, while others feature reduced frost damage altogether. Aside from bumping up all the HP gauges across all classes (they can take more hits now), some classes can even pierce past Frost shields and can counter delaying tactics (slowing down). So what the changes really affect is just the approach against non-Frost-resistant mobs and nothing more.

If they remove the one thing that makes the Frost tree unique, then the tree itself becomes irrelevant. In fact, you could say it becomes a water-related, low-damage and redundant talent tree that serves no more purpose other than to add a tree to two useful ones.  According to Tseric, Blizzard is determined from eliminating the "chain-crit" feat either way. So despite pleas at the WoW Forums, it looks like the Priest class will be getting a new seatmate.