Wigan returned to winning ways following last weekend's defeat to Huddersfield after running riot in the second half against the London Broncos.
Iain Thornley and Josh Charnley went over in the opening 11 minutes but Tomkins was sin-binned for 10 minutes for talking out of turn to the referee and that sparked the visitors into life. They responded with scores from Liam Colbon and Keiran Dixon to silence the DW Stadium crowd.
And when Michael McIlorum and Chad Randall traded scores it looked like London would lead at the break but Warriors captain Sean O'Loughlin went over for the home side to lead 22-18.
Warriors coach Shaun Wane brought back Tomkins at full-back, while Chris Tuson returned from injury to start in the second row with Jack Hughes switching to centre in place of the ill Darrell Goulding.
London made a number of changes following their winless start to the season with Dan Sarginson, Colbon and Michael Channing starting, while coach Tony Rea opted to name his assistant coach and former Catalan Dragons hooker Ben Fisher on the bench.
Wigan took the lead inside two minutes when Thornley touched down in the corner following good work by Pat Richards, Blake Green and Tomkins. The try was converted by Richards for a 6-0 lead.
The Broncos looked to be spurred on from that early setback and it needed a great Charnley tackle to deny Dixon. The visitors refused to lie down and after two successive penalties they thought they had crossed but Dixon dropped the ball as he went over the line.
London were left to rue those missed chances as Wigan extended their lead moments later when Charnley scored for the fourth successive game this season following a swift passing move.
Just as Wigan looked to be taking control they were reduced to 12 men when Tomkins was sent to the sin bin for mouthing off to referee Robert Hicks, and London made the extra man count as former Wigan winger Colbon went in at the corner, Michael Witt converting to reduce the deficit to 10-6.
Wigan were determined not to be behind at the break and they made sure they were not as skipper O'Loughlin powered his way over from close range and with Richards converting they led by four points at half-time.
Wigan opened up the second half like the first with a try for Tomkins. O'Loughlin linked well with Smith and Green before the full-back charged into the line to go over unopposed.
Wigan finally put the game to bed in the 62nd minute when Tomkins broke a tackle in midfield and raced away before sending Green over for his first try in a Warriors shirt. Richards added the extras to make it 38-18.