Warriors lead Conference A, but they were beaten 26-8 by second-placed Conference B outfit Scarlets in Llanelli.
Rhys Patchell went over twice and Leigh Halfpenny kicked eight points to keep the pressure on conference leaders Leinster, who also won.
Benetton are running out of time to reach the play-offs but they did their chances no harm with a bonus-point win over Dragons, although they almost let a commanding lead slip.
The Italian side led 26-6 at the break, but they settled for a narrow 29-27 victory as Dragons fell short in their fightback.
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