The visitors went ahead after just 13 minutes when Gabriel Piccolo’s long ball was flicked on by Kallum Higginbotham to Taylor who found the bottom right-hand corner of the net from 12 yards.
Higginbotham also provided the assist for the second goal which arrived five minutes before the break, when his corner was powerfully headed home at close range by Taylor-Sinclair.
The only black mark for Thistle was the sending-off of Stuart Bannigan who was shown a brace of yellow cards in the space of four minutes, the second of these for a late tackle on Kevin McHattie in the 82nd minute.
Hearts performed better after the break, with Brad McKay heading narrowly over before Callum Tapping lashed an effort against the bar on the hour mark.
However, they were unable to reduce the deficit and are now 19 points adrift at the base of the table after collecting just two points from their last eight league games.