There's definitely something there when it comes to Jed strategy for building bullpens and yes they typically figure it out most years, but its not foolproof either. The Cubs missed the playoffs by 1 game last year and as pointed out overuse played a big part in the late season collapse. Why? Guys like Fulmer and Boxberger battled injuries but in general while they ended up piecing together a solid 7-9 with Merryweather, Leiter and Alzolay, they had issues with depth beyond that, thus Ross felt like he needed to use his horses over and over again. That overuse can be blamed on Ross, but also because the Cubs fell way off the pace in the early part of the season (at least somewhat due to bullpen struggles) and needed to win so many of those close games in July and August to play themselves into playoff positioning.
Basically what I'm trying to say is that while Jed's piecemeal bullpen did become effective for a big chunk of the season, I don't consider the strategy as successful last year because bullpen issues in April, May and September contributed to the Cubs falling 1 game short of the playoffs. If the Cubs fall 1 game short again this year, the 6-7 blown games in April and May this year will be a contributing factor.
I'd say that by nature of how Jed builds bullpens, we should expect some struggles early season most years and build that into our expectations, but when those struggles affect our play in September or the struggles are directly affecting the outcome of such a high percentage of games early in the season, I think its fair to criticize while still acknowledging that Jed and co. have done a solid job overall building bullpens from scraps.