a big part of the sissons signing is that he was a legit valuable part of the Knights' 3rd line for their cup run.
whether it's smart to judge him on a playoffs run is up for debate - but at the same time Sissons has made the playoffs most every year he's been in the league and played more than just a 4th line part in all of those years.
the most common lines for their playoffs run:
Barbashev - Eichel - Dorofyev
Howden - Karlsson - Marner
Hertl - Sissons - Stone
C.Smith - Dowd - Kolesar
I guess there is some debate on whether Sissons or Hertl played more C, though with karlsson's injury they both needed to at times. But I think in general when healthy Sissons was the 3C for the playoffs.
Though Sissons also spent lots of time with Dowd and Smith, with Stone up on the Eichel line and Hertl filling in for Karlsson at 2C.
Playoffs 5v5
C Eichel 22gms, 30.8toi% (-10.0dzs%), 51.4xgf% (+0.9rel), 1.40p1/60, 1.93p/60, 1.67avg
W Barbashev 22gms, 30.8toi% (-8.6toi%), 48.6xgf% (-2.9rel), 1.57p1/60, 2.10p/60, 1.86avg
W Dorofyev 22gms, 25.4toi% (-5.9dzs%), 48.9xgf% (-3.1rel), 1.69p1/60, 1.91p/60, 1.81avg
C Karlsson 15gms, 28.3toi% (+3.4dzs%), 55.4xgf% (+3.2rel), 1.98p1/60, 2.27p/60, 2.13avg
W Marner 22gms, 29.7toi% (-3.4toi%), 53.9xgf% (+1.6rel), 2.18p1/60, 2.54p/60, 2.36avg
W Howden 22gms, 26.8toi% (+0.9dzs%), 53.3xgf% (+1.3rel), 1.81p1/60, 2.62p/60, 2.22avg
C Sissons 22gms, 23.3toi% (+6.9dzs%), 51.2xgf% (-1.2rel), 0.92p1/60, 1.62p/60, 1.28avg
W Stone 17gms, 26.8toi% (-7.5dzs%), 48.4xgf% (-3.7rel), 1.04p1/60, 1.80p/60, 1.42avg
W Hertl 22gms, 19.6toi% (+2.3dzs%), 57.2xgf% (+4.7rel), 1.10p1/60, 1.10p/60, 1.10avg
C Dowd 22gms, 22.3toi% (+10.2dzs%), 50.0xgf% (-1.6rel), 0.48p1/60, 0.73p/60, 0.61avg
W C.Smith 22gms, 21.3toi% (+9.1dzs%), 49.1xgf% (-2.5rel), 0.76p1/60, 1.26p/60, 1.01avg
W Kolesar 21gms, 18.2toi% (+3.8dzs%), 52.9xgf% (-0.1rel), 0.31p/160, 0.31p/60, 0.31avg