The league leaders did their bit, beating arch rivals Munster 22-18 on Saturday as Brian O'Driscoll scored his first try of the RaboDirect PRO12 season.
Ian Madigan added 17 points from the tee as opposite number Ian Keatley's six penalties were not enough for the Munstermen.
And Matt O'Connor's side were handed a boost by struggling Cardiff Blues as the Welsh region beat third-place Ulster 28-23 at Arms Park.
Gareth Davies collected 23 points with his boot and Robin Copeland's try completed Cardiff's scoring, as a Darren Cave try and six Paddy Jackson penalties fell short.
The competition's two Italian sides almost completed a double, as Benetton Treviso beat Edinburgh, but bottom club Zebre were held at home by Newport Gwent Dragons.
The Welsh side crossed the whitewash three times to Zebre's one in Parma but Luciano Orquera sent five penalties between the posts to ensure it finished 25-25.
Scarlets won a thriller on Sunday, edging an eight-try contest with Connacht 32-30 to strengthen their top-half ambitions and deny the visitors a fifth straight RaboDirect PRO12 win.
And Glasgow Warriors won an early battle for fourth, beating Ospreys 11-9 on Friday night with a Tommy Seymour try.
TRY OF THE WEEKEND
With Connacht threatening the hosts' line on Sunday, Scarlets recovered the ball through full-back Liam Williams.
He spread it across to the right flank and found Kristian Phillips who, from nothing, sparked the game's best move.
The winger burst into space and, after powerfully breaking a tackle, sent a perfectly-timed offload to Josh Turnbull to race over the line
BREAK OF THE WEEKEND
With their internationals back in the fold Cardiff Blues downed title-chasing Ulster and it was one of Warren Gatland's men who created the decisive try.
Alex Cuthbert collected the ball on his unfavoured left wing but didn't look at all out of place.
The Wales winger arched inside and with Copeland bursting through, he sent a cheeky back-of-the-hand offload to the No.8 to score.
PLAY OF THE WEEKEND
Jonathan Davies was another Wales man back in RaboDirect PRO12 action and he claimed one of the weekend's best tries.
After Rhys Priestland sent over an accurate missed pass Davies fed Jordan Williams and, after the winger gained 30 yards down the touchline, Davies was waiting on his right shoulder to collect and dot down.
PLAYER OF THE WEEKEND
Given their respective league positions, Cardiff's victory over Ulster goes down as one of the upsets of the season and fly-half Gareth Davies was never far from the action.
As well as pulling the strings in midfield, the 30-year-old was regularly on target from the tee, collecting seven penalties and a conversion to end the Blues' five-match losing run in the competition.
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