Mage: Can't argue with glacial mysteries, this thing screws me over so much when I get it from emerald spellstone. Low cost spells are unfortunate, but this thing takes up precious hand space as well when I get it. To be different though, I'll say ice walker, make it a 2/3. Deck of Wonders could probably draw a card as well.
Paladin: Make chillblade champion a 3/3
Priest: No clue, I'd probably go with 5/6 for benedictus, don't want to change things too quickly, and priest is a class that has tools to outlast already.
Rogue: Make Spectral Pillager a 6/6, or at least a 5/6