Diving into the analytics, Barrie is the anchor on the defensive end (surprising to no one). He manages a >50% xGF only while paired with Nurse and comprises 4 of the bottom 5 defensive combinations with >15 min TOI 5v5 this season (Barrie with Russell 41% xGF, with Koekkeok 39% xGF, with Niemelainen 39% xGF, with Bouchard 27 xGF%). The only worse pairing was Russell Broberg with 6% xGF!!!!.
Nurse and Bouchard are the horses on the back-end, both while paired together and separately. I believe separating them is the best course of action as opposed to playing them together. Together they are pretty damn good tho (~59% xGF in over 350 min TOI 5v5). From simple eye test, Bouchard struggles to stop the cycle so ideally he is partnered with a more physically gifted player.
Ceci seems to be performing adequately (~50% xGF while playing top 4 minutes), but I believe he's better suited to as a #5 guy where I think he would excel (as he did in Pittsburgh).
In an ideal world Keith would retire and open up 9M in cap space, but banking on that is not realistic. He seems to perform better with a puck-mover on his pairing. If he is still here next season, I think you have to pair him with Bouchard, or have him and Ceci (~50 xGF% this year getting top 4 minutes) on the bottom pair getting ~15 min a game.