I definitely think that a lot of the reason we tend to worry about the guys on our favorite team (in this case, the bullpen) is because we see them every day. We see when a guy consistently starts hitters off 2-0 and shakily gets the job done. We see the wildness in and out of the zone that Kimbrel sometimes has. We see this day in and day out with Sox' pitchers. We don't see this with other teams. We don't see the high-wire act that some of them walk. We just look at the dominant numbers and say, wow, that guy is really good.
Looking at b-ref today, here's the stat lines for Kimbrel, Kelly, and Barnes:
Kimbrel: 20.1 ip, 2.21 era, 0.84 whip, 12.4 k/9
Kelly: 21.2 ip, 2.08 era, 0.88 whip, 10.4 k/9
Barnes: 19.2 ip, 2.75 era, 1.12 whip, 12.4 k/9
I mean, that's damned good. I'll compare them to the other top threesomes on other top teams in the AL.
NYY
Chapman: 19.0 ip, 1.42 era, 0.95 whip, 17.1 k/9
Green: 25.0 ip, 2.52 era, 0.96 whip, 12.2 k/9
Robertson: 21.1 ip, 4.22 era, 1.03 whip, 10.5 k/9
Hou
Giles: 15.0 ip, 3.60 era, 0.93 whip, 7.2 k/9
Peacock: 17.2 ip, 1.93 era, 0.86 whip, 12.1 k/9
Devenski: 17.2 ip, 1.53 era, 0.96 whip, 10.7 k/9
Cle
Allen: 19.0 ip, 3.32 era, 1.26 whip, 9.9 k/9
Miller: 12.0 ip, 3.00 era, 1.58 whip, 15.8 k/9
Otero: 16.1 ip, 7.16 era, 1.22 whip, 8.3 k/9
The Sox stack up just fine with these other teams. We just see the warts on our own guys' faces every day, but we don't see it on other teams. We'd all be having a heart attack if Giles was our closer. Or watching Andrew Miller and his 1.58 whip. Or even Robertson with a 4.22 era.
By the way, on the question of worrying about Kimbrel and the HR ball.... I'm convinced that it's almost 100% luck when guys homer off him. His stuff is SO nasty that in order to jack one off him, you have to guess fastball and location and just basically hope you run into one. Occasionally it happens.