What mage class needs (especially wizard) is something like Magic Guard to help with their survivability, which lasts for like 10 minutes or something, and when you get hit 80% of damage gets taken from SP and 20% gets taken from HP. How cool would that be?
Or it could be like an extra health bar where your spirit acts as health until it reaches zero. Maybe having it activated could double SP costs as a way to make it less possible to be invincible.
Dark Waters is an awesome utility spell, the best spell that a wizard has, imo. However, the 25 second cool-down doesn't make it practical for solo training. Maybe if they decreased the cool-down 10 seconds or something a wizard would be able to survive easier, otherwise I think something like Magic Guard is needed.
10 seconds is a little too overpowered in my opinion. Hunter class would complain because their camo takes longer to recharge I believe, despite the fact that I'm pretty sure a wizard's dps and abilities are a bit incomparable to that of a hunter. 15-20 seconds at best might be a bit better.