Why such a sucky event?
There are many possible explanations, but I think the most likely is:
They finally realized that they gave out too much SC. Not only everyone maxed it out, but people can max out even whatever they can exchange for them (whips, runestones). So they just want the players to lose all these SC while gaining nothing in exchange.
Exchange or not?
I wouldn't do it if I were you. Gold is a free resource, we get a virtually unlimited amount. WB, DI and sylph boss gives many millions each day. If you are a relatively new player, with far from max stables, SC is your only chance to catch up with the older servers with whips. So you can do nothing just wait and hope. Older players, prolly you don't need gold anyway. So wait is a good strat too. When your mail is about to expire, just loot it, get kicked and that's it.
Is it wise what Wartune does?
No, not at all. It's never wise to piss off your customers because you can lose them. In my other favorite game, Doomlord, they don't nerf, don't reduce rewards, and you have an event calendar for the entire year. Players feel safe and are happy.
And this is why because there WILL be a better SC event eventually. Because the player community CAN create a pressure on them, it will just take some time. But until then, don't worry to much about it. A better SC event will come eventually.
The gem event
There is also a gem event coming tomorrow. It's the same as before - it's limited (can be done only once per day), gives runestones. The change is they removed lvl 5 gem reward, and added lvl 9 and lvl 10.
This event is good! Actually - since most of us made lvl 9-10 gems for HoF and other advantages, an unlimited gem event with lvl 9-10 gems would be really shocking when we realize how much we lost by not being patient enough :)
Finally some math:
1. If you have a few lvl 9 and lvl 8 gems, you need a total of 112 lvl 4 gems each day to claim all rewards and end up with 2 lvl 10 gems.
2. In the old unlimited event (where you get double reward for every gem, incl. lvl 5, but no rew for lvl 8 and 9), if you started with 112 lvl 4 gems (and also had 1 lvl 8 and lvl 9 gem), you ended up with 1.3 lvl 10 gems.
So actually, the current event is better than the previous one :) You should claim each reward each day if you have the gems.