John van't Schip's side travelled to the Westpac Stadium on the back of three wins and a draw in their last four league outings - a complete turnaround from their early season form, that saw them fail to win any of their opening 14 matches.
And the Heart picked up another three points on Sunday, with in-form striker David Williams - who scored late winners in their previous two fixtures - notching a hat-trick to take his A-League tally to nine for the season.
Dutch midfielder Orlando Engelaar got the visitors off to a flyer by putting them ahead after just nine minutes, before Williams scored his first of the match 10 minutes later.
Heart had to wait until six minutes into the second half to all but secure the victory courtesy of Williams, before things went from bad to worse for Phoenix as goalkeeper Glen Moss put through his own net shortly after.
Williams promptly rounded off the rout just after the hour mark, moving Van't Schip's men to within three points of ninth-placed Perth Glory.
In Sunday's other A-League fixture, struggling Newcastle Jets ended a seven-game winless run with a shock 1-0 victory at leaders Brisbane Roar.
Adam Taggart's 59th-minute penalty was enough for the away side at Suncorp Stadium, with the Roar missing the opportunity to extend their seven-point advantage over Western Sydney Wanderers.
