IF SS2 was meant to save time, why not reset CDs every new start?

[Zaranghae]

Because it doesn't work that way. Someone at fan fest asked if Square could make CDs not kick in when switching classes and the reply was "We have that restriction for balance reasons." I don't think it would be that simple to make Stoneskin the only spell that makes the global CD instant. Besides, you'd still be going faster just making the spell AOE than to click on each person.

iirc, the balance reason was because if you switched classes in open world and only for open world, then you would be able to spam certain CDs such as switch off with another player to kill a monster by spamming hallowed ground back and forth (this would be possible to kill an S rank monster with only 2 players). Also, I do not understand the latter statements. For example if your party wipes within 30 seconds but you spammed all your 120-300 second CDs, you'd have to wait for that longer and feel probably even more frustration not to screw up next time.