If you are dropping the standard from top 2 to top 3 then yes of course it looks better as I see both Barrie and Muzzin as good #3s (ie second pair).
To be honest I think 1-2-3-4 and top pair 2nd pair are bad ways of classifying defensemen. 1-2-3-4 creates distinctions that aren't there, and pairings are objectives, a mix of 2 guys of different skill levels that can get a job done against different competition.
If I had to use #'s/ labels
#'1 / - they can carry the mail against the best with a bottom pair partner, very few in the league
#2/3- Can either drive play offensively or are good enough that one of them + a 4/5 can make a viable top pairing, two of them together makes a damn good top pairing
#4/5 - Can complement a 2/3 to make a viable top pair, can carry a 6/7 to make a viable 2nd pair, two of them makes a damn good 2nd pair
6-7 no explanation need
IMO Rielly/Barrie/Muzzin are all in that 2/3 group, with Dermott & Ceci hopefully emerging as 4/5's. If you add another 4/5 to the group I don't see how it's below average.
Rielly has shown the ability to make a viable top pairing with a 4/5 type.
Muzzin+Barrie would be a viable top pair
Leaving Ceci+ Dermott as a potentially ++ level 3rd pair