Single target spells aren't a major issue (at least with just one of these in play)... mass CC spells are.
Lightning storm becomes firestorm with one of these in play. I think mass CC just gets too powerful with this. It lets you wipe the field for about 2 quanta... I shudder to think about the voodoo dryspell combo.
Comboed with voodoo dolls the upped version is clearly more powerful.
Heavily buffing mass CC cards upstets the balance of the game a bit too much for my tastes. It overly favors
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and
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which can defend against it easily.
The upped version is a little more tame. It adds a pretty big boost to direct damage though. The fractal combo may be a little too abusable with such a low casting cost. At 3
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for +5 damage the fractal fire bolt combo is bit too strong.
I do hope you only mean for this to apply to spell cards and not all spell damage. SoW and psions don't need that kind of a buff!
I do like the idea of making spell slinger decks a bit more competitive but this card probably needs a little balancing so it won't make them OP.