Gorilla is right on point 2; the mob spawn is so slow compare to odawa cave. Especially when you have to buy Sos to get in, money 12sky2 Gold is spend, so we can get in the 3X or 4X exp but the mob spawn is so slow, we have to gather them and time is wasted especially if you are on P+C X or PET. Better to grind in odawa than Sos even with the extra exp promo.
You would gain more Twelvesky2 exp in odawa than in Sos cos in Odawa, the mobs spawn faster and in sos they spawn so slowly. Less exp is gain even if 3X or 4X exp is given. And also every time when Sos promo is on the maps lagg bad till you can not repill and die. No exp lost but the time to run back to the same island and grind waste a lot of time. If this can be fixing we are sure more will join in Sos to gain exp and pet exp.