Thornton matched his goal total from last season.
"He can shoot the puck as well, and you saw that tonight," Sharks forward Joe Pavelski said. "Those were a couple big goals for us. When we make those plays and he's pulling the trigger, that's really good."
Hertl had a power-play goal, and Timo Meier also scored for San Jose (18-11-4).
Brendan Gaunce, Jake Virtanen, Brock Boeser and Daniel Sedin scored for Vancouver (15-16-5), which lost for the seventh time in its past eight games (1-6-1).
"A point's big, but we definitely feel we could've won that game," Boeser said. "Obviously we need to clean up some special teams there."
San Jose moved ahead 4-3 when Hertl scored on a 5-on-3 at 18:56 of the second period, but Sedin answered with a goal from the right circle at 2:09 of the third to make it 4-4.
"I loved the way we played tonight minus our penalty killing," Canucks coach Travis Green said. "You score four goals on the road, you come back a couple of times, that's the kind of game we want to play. If we play that way every night we're going to be fine."