Crafts

[Ruvanal]

Actually no

King's and Merciless have the same affix group - you can only get one of them

Actually yes,
Merciless group=105
King's group=111
Different groups numbers so they can stack together. This was the sought after pair for rare weapons in the pre-LoD game (perfect would have netted 200% damage).

If I were to do a bloodcraft (30-60% ED) on a tomahawk, could I get Merciless (81-100% ED)?
For a tomahawk, if the resulting ilvl was 59+ it would have a chance to get the Merciless prefix (crafted or rare). If the the ilvl was 78+ it would also have a chance to get the King's prefix (again crafted or rare). It would be possible that you could get both of these on the same crafted item in addition to the crafts 30-60% ED.