The Giants ended a 51-year wait for a win at Headingley 12 months ago and once more had the measure of their opponents as they condemned them to back-to-back defeats in front of new England rugby union coach Stuart Lancaster.
Leeds, without five internationals through injury and illness, took the lead with Zak Hardaker's 25th-minute try but the visitors replied through Greg Eden, Jermaine McGillvary, Jason Chan and Eorl Crabtree before Kylie Leuluai grabbed a consolation try.
Leeds will also be consoled by the performance of 18-year-old Stevie Ward, who was given his full debut at scrum-half in the absence of Danny McGuire and Rob Burrow and acquitted himself well.
Huddersfield, who had Australian forward Luke O'Donnell playing his first match for seven months after undergoing major knee surgery, were the livelier side from the start, with Danny Brough kicking intelligently while strong running from David Fa'alogo and Chan put the Rhinos defence under strain.
Warrington's biggest crowd for 38 years saw the Saints follow up their 46-6 thrashing of champions Leeds with another impressive showing for caretaker coaches Mike Rush and Keiron Cunningham.
Winger Ade Gardner crossed within the opening two minutes, full-back Paul Wellens grabbed two tries in six minutes and Francis Meli continued the early blitz against a shellshocked Wolves. Jonny Lomax also booted over three goals from four attempts to put the Saints in total control at 22-0.
Brett Hodgson and Joel Monaghan grabbed tries for the home side either side of half-time to give them faint hopes of a comeback, but it was to be Saints' night as Sia Soliola crashed over 12 minutes from time to make the game safe.
Centre Darrell Goulding, who scored five tries for the City Reds while on loan in 2009, led the way with a first-half double as the Warriors responded to last week's last-gap defeat to Warrington.
Sam Tomkins also scored a brace of tries, with additions from Josh Charnley, George Carmont, Liam Farrell and Matthew Russell for the Warriors, while Charnley added four goals.
Daniel Holdsworth and Danny Williams each scored a first-half try for the home side and Luke Patten and Jordan James crossed in the second half with two successful Holdsworth conversions.
The Bulls battled gamely, but Tom Briscoe's try with 10 minutes left proved decisive, in a match that could be the four-time Super League champions' last before they are plunged into administration.
Richard Horne scored a brace for the home side and Willie Manu recorded his own try with Danny Tickle adding the extras, while Keith Lulia and Karl Pryce crossed over for the Bulls before a memorable John Bateman try had levelled the scores at 18-18 with 14 minutes left - but Hull stole ahead through Briscoe before Tickle landed a late penalty.
The Tigers looked to be heading for their eighth successive defeat when they trailed 30-22, but they staged a great recovery to achieve their first home win of the season. Hull KR's defeat was particularly hard on centre Kris Welham, who scored three tries in a pulsating match at Probiz Coliseum.
Youngquest claimed another try for the Tigers in addition to tries from Josh Griffin, Richard Owen, Kirk Dixon and Danny Orr with Dixon kicking over five goals. While Josh Hodgson and Lincoln Withers also scored a try apiece for Rovers as Michael Dobson added the extras.