100% fail is correct. If your HP reaches 0, you die...same works for crafting.

Also, overkill is allowed in every FF game until now...same works for cfarting.

Keeping durability is part of the challenge of crafting here. If 0dura/100% was allowed, people wouldn't care much about unstable and would spam rapid in the end regardless of durability.

Also, allowing 0/100% would generate a much more frustrating situation...if you can complete a synth this way it would be good for materials and leves only...because once the finished item enter in touch up mode it would automatically break due 0 dura.

Complaining about this is the same of complaining a cactuar r20 killed your r50 class. Its part of the game...just assume it might happen and move foward ^^