When it is defined a Decision Table with rows don't covering all possible ranges, the message reported by workbench isn't clear, in fact it is a wrong message:
"Deficient rule has actions which conflict with another rule and conditions that do not overlap with the other rule."
"Since the deficient rule can fire at the same time as an another rule, it is impossible to know which actions end up activating last. This causes the rule set to be inconsistent. To fix this, please either remove the deficient rule or make the conditions more strict."
The message above seems generic for cases that two rules can fire while it is expect them to be exclusive, but it is confuse for rows out-of-range.