You can clone with
1) When you overlay with powder, it leaves a block of air first and then overlays. All blocks overlaid with powder should be exactly one y level lower than they are now (currently you have to tediously use gravel first, let it fall, then change it into what you want...)
2) when "/b over all" mode is turned on, the depth parameter stops working. E.g., if I have "all" mode on, and depth = 3, it will just act as if depth was set to 1 instead. Both should be able to work simultaneously.
update: when "all" mode is on, splatter overlay also stops growing (i.e., growth parameter doesn't matter, just creates one block at every seed only)
If you found two bugs, why don't you create two issues?
Well they both had to do with depth problems in the exact same brush... so quite possibly related.