Seems like you solve that problem by putting Dermott with Holl and Liljegren with Muzzin, which is what it should have been from the start.
Dermott plays well with guys like Holl: played well with Bogosian, played well with Muzzin even when he was on his offside, and he even played well with Holl himself last year. He is playing well on his offside with Sandin too, but we are tossing them soft minutes. We can bump up Dermott's minutes a bit and have 3 solid pairings, and it doesn't even stop Keefe from double-shifting Muzzin and Holl together at times.
Liljegren's skating ability covers for Muzzin's weaknesses a lot better than Holl, and Liljegren is a refined defensive talent in his own right. Sandin has done well in a sheltered offensive role, but that is not what the Leafs need right now... And I fully believe that Liljegren can provide the same kind of PP value as Sandin if you need a 2PP replacement.