Virulent Quicksand should keep its gravity as a sand block, but other than that the logic behind the blindness while inside the block is not suitable anymore.
This is because it breaks when the entity is not standing on a full sized block and it needs revision.

Since gravity would likely want to be reimplemented it should be noted that world generation about it should be tweaked as well

As of now gravity won't be reimplemented, block rendering is now properly displayed like Powder Snow.