Both are good, just if you use orb remember to put at least 17 into cold mastery, and max its only synergy.
(57 point cost)
This makes it ideal for energy shield since Tele u need at least 17-18 and say 10-15 for energy shield ( 27-33 points)
If you want maximum damage, and dont mind loosing a bit of control then go blizzard, you will get lots more damage too.
Both have PvP pros and cons - with Orb it can be resisted to a heavy degree - Blizzard is a lot harder to resist.
On that note, its easier to hit ppl with Orb, as it spams all over the place, and harder to hit with Blizz, since if they can just TP out of there.
Personal preference.
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No, I dont reccomend using both.
Both are timed spells, if you use 2 spells, make sure one is timed, and one is based on Fast Cast - this way you can spam your timed one, flick to the fast cast one, spam a few of them, then go back to the timed one.
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If you max blizzard you will have to opt for a cold armor as you wont have the points to spare for energy shield - so its personal preference.
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Most important thing is to get that cold mastery up to at least 17 with bonuses to plus skills - with cold damage, the actual damage in the character window is misleading - as cold mastery reduces enemy resistnaces therefore making opponents take more damage.
If you do PvP max cold mastery.
