Kraev was the architect of Wellington's dominance at UTAS Stadium in Launceston on Friday night, playing a key role in two goals and scoring another in the rout.
The Bulgarian playmaker doubled the lead in the second half after Sasse's early opener.
Oskar Zawada rounded out the scoring, becoming the first Phoenix player to score from the penalty spot this season following the side's four previous misses.
The goals continued Wellington's run of scoring in every match throughout the campaign but it was a third clean sheet that would have given coach Ufuk Talay most cause for optimism.
The result snapped a run of three matches without a win and lifted the Phoenix to fifth spot.
It was another dagger in Western United's championship defence, with John Aloisi's side now having won just once in their last eight games.
They sit second from bottom - just two points ahead of Melbourne Victory, who have two games in hand - and are seven points outside the top six.
Western United goalkeeper Jamie Young denied Sasse an opener in the 10th minute with a fine close-range save after the Brazilian midfielder had been played in by Kraev.
But Sasse grabbed his next chance, finishing a sweeping end-to-end move in the 19th minute when he took another pass from Kraev, cut inside with two touches and smashed a powerful left-foot shot into the bottom corner from outside the box.
It was a strike Sasse relished after he was one of two Phoenix players who missed from the penalty spot in the previous week's defeat to Macarthur.
Kraev found the net himself in the 58th minute when he received the ball just inside his own half and charged forward to curl home a sweet right-foot shot from outside the box.
He then won the penalty when he was clumsily brought down by Tongo Doumbia and Zawada - who, like Sasse, missed from the spot last week - was successful this time despite Young getting a hand to the shot.
Oliver Sail preserved Wellington's clean sheet with a fine close-range save from Lachie Walers in the 78th minute.
Zawada should have scored a fourth for the Phoenix when he went clean through on goal in stoppage time but was denied again by Young.
It was Western United's first loss in six matches at their 'home away from home' in Launceston.
