I'll agree Diffley deserves some ice time, unless there's something going on in practice/injury that we don't know about. Both Diffley and Switzer, no. They've played D at the same time three times, @UVM and Yale when Fabbro was at Canadian tryouts and the Union game. The first two games I remember them playing fine but nothing memorable, Yale is/was not a good team. Both were significantly overmatched by Union forwards. Of course Shane put one in against Union but that's not a contribution the coaching staff could reasonably count on with any regularity.
If you want to argue McAvoy needs to realize that he's played B-/B hockey of late, which isn't "bad" per se, but is capable of being one of the best D in the country then I'll agree with that 100%. I don't think that warrants him being benched in favor of Switzer or Diffley unless his play continues to regress. But he's gotta realize he's the best blueliner out there every night and he's gotta play like it, whether that means getting on the scoresheet himself, making a play in his own zone that springs one of his forwards into an offensive chance, or knocking an opposing forward down to get the team riled up. He doesn't wear a letter but he's the starting point guard and most important skater on the team, he's gotta play like it. B- play from him isn't enough to get us where we want to go.
A change I'd like to see is actually breaking up Fabbro and Hickey, their playing style is so similar that it's a redundant pairing. Perhaps matching one with Doyle and one with MacLeod/Diffley/Switzer might be worth a look.
Also the most recent weather reports have the snow ending in the very early afternoon tomorrow so Beanpot Tuesday might not be necessary.