Pulled draft data from B-R for the 1st 30 picks from 2007 (Moore’s first draft) until 2018 (giving teams/players credit for being in the system for up to 3 years). From there, aggregated up to get averages by group of 5 (picks 1-5, picks 6-10 etc.) and then got it to an average per year. If you’re curious, someone drafted with picks 1-5 should average 1.38 WAR per year from their draft; someone drafted in picks 26-30 average 0.14 WAR/year (the difference is pretty interesting in and of itself — and incidentally there is a big drop basically from picks 20-25 to 26-30).
Long story short, when looking at players KCR have drafted in total, they are last in the MLB in observed WAR vs. expected, with -49.1 less than what they should have based on when (what year) and where (what pick) their players were drafted.
The top of the food chain is Angels (73.4, mainly driven by Trout), Nationals (58.1, Harper/Rendon/Strasburg), Astros (55.2, Correa/Springer/Bregman) and Giants (52.8, Posey/Bumgarner/Z. Wheeler).
KCR is actually hit harder with hitters than pitchers, at a -37.1 rate for hitters.
Obviously they hit decently on Hosmer and Moustakas, but not well enough to cover for Colon, Starling and Dozier (which is interesting and I’m a big Dozier guy but he still has a negative WAR and was drafted in 2013). The fact that 4 of them were top 5 picks doesn’t help either — Moustakas and Hosmer come in at about expected, and the other 3 are well below.
The Pirates and Rays are below them — but jump them in overall because of moderate (Pirates) to solid (Rays) success with pitching.
KCR has missed on pitching as well (as we know).
That said, by virtue of where they were drafted (late 10’s) and the moderate success they had, Crow, Finnegan and Singer buoy the -8+ Zimmer contributes (the others who qualify, Griffin and Ashe Russell, were drafted low enough that their expected wasn’t that much anyway).