No mistake, the posted drop rates are correct. Rates for either get doubled every once in a while during 2x events but what you see now (91.5%/8%/0.5%) are the normal percentages. 

So  there  is  no  actual increased  value for void crystals?

Void shards always draw void champs. So you won't draw just normal champs. Void champs are generally better than their counterparts at the same level. You cannot draw voids champs from any other shard. So void shards are better, despite having the same rates because you have a chance for better champs.