The Tigers could also have a major headache this week with centre Chris Lawrence, who suffered an horrendous hip dislocation early in the season, leaving the field with an apparent hamstring injury after a long run for the match-clinching try.
Back-rower Liam Fulton was also placed on report for a 69th-minute high shot on Dragons winger Jason Nightingale.
The Tigers broke a four-match losing steak against the Dragons, continuing their stunning return to form as the business end of the season looms, while the Dragons remain outside the top four.
For the Tigers, Fulton, Marshall and Beau Ryan scored four-pointers with Marshall kicking two from four.
Darius Boyd and Brett Morris scored tries for the Dragons with Soward booting two and Ben Hornby one from the sideline.
St George Illawarra led 2-0 after a first half the Tigers probably had the better of through a 37th-minute Soward penalty goal.
They extended their lead with the game's first try in the 47th minute, Boyd capitalising on Dragons-bound fullback Tim Moltzen spilling a Soward bomb and the conversion making it 8-0.
But it was 8-6 in the 61st minute when Fulton leapt to grab a Robbie Farah cross-field kick and slammed the ball down, Marshall adding the extras.
The best was yet to come five minutes later when Marshall started and finished an 80m move and the Tigers were in front 12-8.
A clever cut-out pass from Boyd sent Morris over on the back of the penalty for Fulton's high shot in the 71st minute before part-timer Hornby's stunning sideline conversion and the Dragons were back in front 14-12.
Their lead lasted less than five minutes, though, when Marshall's quick hands sent Lawrence away and Ryan backed up to complete the 70m effort.
WESTS TIGERS 16 (L Fulton B Marshall B Ryan tries B Marshall 2 goals) bt ST GEORGE ILLAWARRA 14 (D Boyd B Morris tries J Soward 2 B Hornby goals) at Sydney Football Stadium. Referee: Tony Archer, Shayne Hayne. Crowd: 27,687.
-AAP
