Frost Chanelling Overrated?Follow

Hi, i'm a n00b to warcraft and only have 1 character who's level 46 and still know very little. I've been following the worlds greatest mage post and have been impressed with it. However this is what i see for the frost channeling talent:-

Frost Channeling (3) - Reduces the mana cost of all spells by 10% and reduces the threat caused by your Frost spells by 10%.

R: A
S: A
P: A

This makes the efficiency of the Frost tree as far as mana goes truly shine, add in the reduced threat, and you have a very solid PvE talent. Not as great in PvP, as the reduced threat does nothing, but it can save you some mana, which has become an important factor in ye olde arenas.
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Now i'd like some explanation as to how this talent is rated so highly, i can't see you finishing up on the deal with this talent because your spells have a reduced threat & the mana you would of saved ends up having to be used on an extra 1 or 2 spells to kill your enemy anyway, my original thought was that this is a break-even deal but on 2nd thought its not, you finish 3 talent points down and without much to show for it atall.

Can somebody please shed some light on this subject & clue me in on what i'm missing here

Look at it this way: If you have a Mana pool of 10,000, Frost chanelling essentially gives you a mana pool of 11,000. Not exactly, but close enough for illustrative purposes.

The threat reduction is incidental, and not really useful at this stage, seeing as nobody raids as frost ;-)

It's a damn fine talent ;-)