Well, since recovery no longer requires more than the daily useage of one food & water, resources will last much longer anyhow.
And it makes sense since the other Artifact dice go from D6 and upp.
The D4 was the odd one out.
Yes. The only use for the D4 in the game was as a resource die, and even there it was not entirely needed. As we could not have more than 12 dice in the dice set, we decided to drop the D4.