When's the last time Detroit or New Jersey didn't have their players go through the minors? Or how about Buffalo and Nashville?
All of those organizations have an unwritten policy that all their players should play at least a year in the minors. Has it hurt anyone's development? No. Has any prospect in any of those four organizations ever demanded a trade because they weren't playing in the NHL? No. Euros will not run away, Patric Hornqvist just played a season in Milwaukee before this season and he is doing great now.
Brian Burke had Bobby Ryan in the minors for a year and a half, did he come out any worse for wear? No.
When guys like Shea Weber, Ryan Suter, Thomas Vanek, Zach Parise and Derek Roy spend a year in the minors before making the big club, and seeing the developmental track record of BUF, NSH, DET and NJD, how can you say the minors are bad for any prospect short of a #1 draft pick (and I mean that literally because I mentioned Bobby Ryan)?
Are the Oilers going to be pushing for a playoff spot next year or contending? Probably not. So what's the harm in having Eberle build his game up in the minors for at least half a season.
All of the previously mentioned teams weren't necessarily doing amazing when they decided to put their top prospects in the minor for seasoning, but they realized it was better for their development. Phoenix is a prime example, they just realized you can't just rush your prospects to the NHL or their development will be severely stunted. I hope the Oilers don't have to go down the same path.
I'm not going to bother replying to every point as I am in a rush.
Pittsburgh, Washington, and Chicago all don't follow the Detroit method and they seem to be doing pretty well.
A lot of the players you mentioned were forced to spend a year in the A because of the lockout. And while you can point to other names that legitimately benefited from AHL time, I can point you to guys who skipped the A with no adverse effects at all.