Yeah, no way in hell they expected fans to like Reigns at #30. There was no story reason for him to be there. They have teased other, more popular choices that could have filled that spot. And even on the pre-show they talked about how "wide open" the Rumble was this year. Which is barely concealed code for the "I'm so glad Roman Reigns isn't in the Rumble again" comments everyone has been making. Reigns got CRAPPED on the past 2 years. I like the guy, but it takes him months to recover from the backlash of his Rumble appearances each year. They put him in, and in that spot, KNOWING it would piss off fans to no end.
The most charitable reason I can think of, short of outright spite, is the plan was for Orton to win all along, and they knew fans would be lukewarm to that. So they threw Roman out to take the heat because they knew Orton would get the boost in cheers they wanted for the winner by eliminating Roman.