Dex is -1% cooldown per 30 dex.
Basically, only noticable if you max it, or on the level 60 skills.
Or if you're playing Lime, who gets 6 300 second cooltime skills. A max dex lime should, theoretically, only wait 30-45 seconds between using his last transform before he can use the first one he used again.
Of course, limes focus on STR because of the massive damage bonus, but if a Lime could max both...
Also, on a Dainn, holding S recovers 1/7th of your mp each second - i.e. Heals all mp from 0 in 7 seconds. No matter WHAT max mp you have
700 mp will get 100/sec, 1400 will get 200/sec.
Of course, because I can spam all my skills before my mp runs dry, I don't care much about my max - Spam, icewall + hold s to restore, repeat. I (Theoretically* never actually see the 0 mp animation, except when I'm not paying attention.