I think its because of the ever increasing shards when you drop. So yes, 4*'s kinda suck, but at the same token I used to get way more regular souls. At least 4* you can level up cheaply to give you level V sacs. But the kicker is that once you drop those you get mythical shards, which are the ones that you really want to nab those chars you really want.
Personally I get that there isnt nearly as many SS's, but for those of us still hunting for a heap of chars, the new system is actually better. And this event seems to allow a nice 'roll' with the resulting hearts.
Im not actually sure if the sac changes have made that much of an inflation issue. And with the ironite rewards - That alone is much more valuable than SS imo. At least until you get to the point where you want to be sharding hundreds of 5* toons. But in aqcuisition, I can make do sharding only good chars that come my way (like the crusader I just got in the first round of saccing).
The only bit I dont relly like is the gold reward bit. It kinda sucks when you land it as in relative terms its probably the least valuable reward imo.
Edit: Also, just got 9 SS from a vortex, so looks like you can still accrue them, just perhaps not as fast...