With just a few watershards this can get out of hand. There is plenty of places to use 2 slow spells and no reason to take away 50% of an enemy's initiative. But, as with most things, people won't complain until the AI starts doing it to them....
But I LIIIIIIIKE being able to roflstomp the compies! 
Seriously though, I feel like haste and slow are the only 2 spells that make a non-fire mage useful. IMO, their initial bonuses/maluses are fine, they just scale too well. Don't make my poor, clumsy mage sovereign even more useless!
