The cubs bullpen has the 13th best ERA in baseball at 3.70. Only teams with better ERAs are KC, BAL, LAD, WAS, HOU, SEA, CLE, NYM, CHI, BOS, MIA and SF. And to be honest it's not even that wide a gap. The difference between the cubs and #5 Houston(3.22) is half a run. Additionally, the schedule for the next bit is fairly brutal. From june 17th through July 10th(All-star break) cubs play 24 straight days. If their starters don't go deep the bullpen is going to look bad because they aren't going to get rest. They need a guy who can get lefties out but people are blowing the need way out of proportion. They've given up 83 earned in 202.0 innings. The breakdown of that is as follows
Justin Grimm - 18 ER 26.2 IP
Adam Warren - 13 ER 25.2 IP
Trevor Cahill - 10 ER 32.2 IP
Pedro Strop - 10 ER 30.1 IP
Clayton Richard - 10 ER 12.1 IP
Travis Wood - 8 ER 31.0 IP
Hector Rondon - 4 ER 26.0 IP
Neil Ramirez - 4 ER 7.2 IP
Spencer Patton - 3 ER 4.0 IP
Carl Edwards Jr. - 1 ER 2.2 IP
Gerardo Concepcion - 1 ER 2.1 IP
Joel Peralta - 1 ER 0.2 IP
If we assume at some point soon Richard is gone and exclude Ramirez as he's no longer with the organization you're talking about 69 runs in 182.0 IP or a 3.41 ERA. If you also ditch Grimm or he just gets better that's down to 51 runs in 155.1 IP or a 2.96 ERA. Top 3 bullpens are KC(2.77), O's(2.91) and Dodgers(3.02). The majority of Richard's time was vs lefties(36 of 63 batters faced 57%). Whoever replaces Richard is going to see the bulk of lefties. Only one other pitcher has seen 40% or more lefties and that's Wood at 52%. Richard was by definition a lefty specialist albeit not a very good one. Replacing that with a Chapman or Miller just doesn't make sense to me. You're not going to burn one of those two for 1 tough lefty in a line up the way you would a lefty specialist and as mentioned Wood is the only other reliever you have that predominantly pitches to lefties.
That's why they strike me as overkill. Undoubtedly they are good pitchers but the reason they make so much money is you pay them to get through the 8th/9th not to get one out when your starter gets into a jam and a lefty comes up. It's an entirely different role that what Richard was here for.