While your point about the Canes not scoring at the rate of expected goals is valid (albeit small sample size), you are interpreting the chart/data incorrectly. It's not Goals/GP it's G/60. Canes are at 2.4 Goals/60.
These numbers are affected by small sample size right now though. Over the past 3 seasons combined, the Canes are the 8th best team in the NHL for 5v5 GF/60 at 2.87 and the best at xGF/60 at 3.04, so they were only 0.17 off the expected. Given the Canes had about 48 minutes of 5v5 time per game, that equates to being short 1 goal every 8 games.
5v5 doesn't really concern me. In the playoffs, it's been the special teams, and sometimes goaltending that has been the issue. Gotta figure out why they are good in the regular season and not good in the playoffs.