Wasps consolidated their place atop Pool 3 and a home Amlin Challenge Cup quarter-final thanks to a 20-19 win over the Dragons.
The visitors were already assured of a place in the play-offs, but missed out on a valuable bonus point that would've improved their ranking for the next round.
The Dragons hit the front first courtesy of an early penalty from former Wasps full-back Tom Prydie, before Nick Robinson levelled proceedings in the 21st minute.
Daniel Evans then crossed the whitewash for the home side with Prydie adding the conversion to give his side a handy 10-3 lead.
Robinson cut the deficit to four points with his second penalty of the night and was then on hand to add the extras to a penalty try on the stroke of half-time that gave Wasps the lead for the first time in the match.
However, the Dragons had the final say of the first half courtesy of another Prydie kick.
Wasps then stretched their lead to 20-16 just before the hour when Robinson converted his own try.
Steffan Jones came off the bench to kick the home side to within a point of their opponents with five minutes left to play, but they were unable to find another score to snatch the victory.
Meanwhile, Perpignan became the fourth side to qualify for the Amlin Challenge Cup quarter-finals after recording a comprehensive 40-22 victory over Femi-CZ Rovigo at the Stade Aimé Giral.
The French giants had the four-try bonus point in the bag by half-time, meaning the comeback that Rovigo needed to help prolong Worcester's qualification hopes was never on the cards.
Even if the English outfit pick up maximum points against Bizkaia Gernika RT on Sunday, Perpignan will pip them to top spot in Pool 2 as they scored more tries in their double header back in December.