The -135s PMCs also make the landing phase difficult. Each Power Mngment Control isn't fully active below 70% N1...also known as every approach ever flown. So each of the 4 throttles are commanding some goofy fuel flow/power setting. Tanker dudes get used to this abnormality by (usually) only adjusting two sym throttles at a time, allowing the resulting power change to take effect, and then fixing it again when it's all jacked up. Guys who try to keep the throttles aligned, or worse, keep adjusting all 4 throttles constantly, get unstable on final with PIO due to the the swept wing & underslung engines. The experienced tanker dude known the PMC hate him and hate each other below 70% N1...and waits to see what he gets. The known power setting is a place from which to deviate.
I agree with the above Google find on the MD. The MD-11's inception has some undertones of the 737 Max issues. The DC-10/MD-10 was the original design, so MD stretched the fuselage out 40', and then had to make the rudder smaller due to CG issues with the new longer moment arm. Then MD put more powerful engines on it. So the flying characteristics weren't the same as a -10, but wait, we'll just add some automation/bells/whistles (LSAS, parallelt rudder) to compensate for the pilots. The single MD-11 type rating allows pilots to fly the -11 and both flavors of MD-10 (MD-10-10, and MD-10-30, the -30 is the KC-10). Does this sound somewhat familiar?
MD-11 wing design is also an issue. I haven't flown the T-38, but I understand that short stubby wings like to go fast, don't like to go slow. MD-11 wings are similar in that respect. The Boeing wings are all kinda the same; big, fat cambered bars that can generate lift throughout a wide range of speeds (although this design does limit the top speed of the airplane). The MD's wings are closer in design to a fighter aircraft; thinner, swept back. This provides a higher top end speed, but also squirrelly characteristics down low on final...high deck angle, higher approach speeds than are normal to transport category aircraft. VVI=GS/2, so with approach speeds in the high 170s when heavy, the VVI is 800' down, vice 700' down. A comparatively small performance window.
Throw in some gusty winds, transitioning out of a low ceiling at max gross landing weight, and you get the picture. I'll say this...the MD has definitely earned its horrific accident history. It's not just 3rd world, barely trained pilots who have trouble processing the automation/landing characteristics on the MD either. Google FX80 @ Narita.
I speak only for myself...the MD is the most difficult plane I've learned to fly. It's overengineered, This airplane, as built, would not be certified by today's standards.
So FedEx trying to handpick guys to manage that monster right out of the gate doesn't seem crazy to me. But choosing C-17 background who fly on the backside of the power curve and add power to flare seems backward. And choosing USN 3-wire trap dudes seems equally incorrect. But they don't pay me to make those decisions.