cold spell speed question

[AtomicKitKat]

Hmm, not too sure about the damage now that you mentioned it. You could always try hiring an Act 3 Cold merc and see if his GS kills more than one target at a time(he uses both spells at random, in addition to frozen armour)

Also, the speed of the relative projectiles is noticeable. As an experiment, try flinging as many IBs as you can before the first one leaves the screen. Then do the same with GS. Let's recap:

Ice Blast:

+ Better damage to mana ratio(barring area damage on GS)
+ Always cheaper to cast.
+ Available sooner(not an issue for you of course)
- Only one target at a time
- Slower

Glacial Spike:

+ Moves faster(5 GS for every 4 IBs, in theory) allowing more consistent freezelock
+ Area of effect ensures it can freezelock up to about 8 monsters at a time
+ Might do area of effect damage as well(which would make IB's damage look bad in comparison)
+ If it hits a wall, the splash can still freeze(possibly damage) nearby monsters.
- More expensive
- Might only do damage to a single target, which would make it worth less(not worthless)

Okay, I hope that's enough information for you. I might go fool around with a character editor to test the AoE of GS and whether damage carries over.