I figure that a hunt's first puzzle sets a team's mood for the first few hours of the hunt; front-load the hunt with an easier puzzle so players get an early morale boost. I also like an easier puzzle at the end so that when players emerge from their puzzling frenzy and reflect on whether they enjoyed themselves, they remember the triumph of crushing that last puzzle.
Some folks like steadily increasing difficulty so that newer teams can see lots of puzzles they can handle. I used to think that way—and I still like the idea of the overall trend-line getting more difficult—but I kinda like alternating between easier and tougher puzzles. Two tough slog-puzzles, one right after the other, can be a downer. An easy-breezy puzzle in between can lift your mood.
So… "overall trend-line getting more difficult"… maybe I shouldn't say I like an "easier puzzle at the end" in the sense of "easiest", but, uhm, like easier than the penultimate puzzle. Maybe the last puzzle is a "medium", but it feels like you crushed it because the next-to-last was a monster.
Maybe that's part of the reason I've been liking minis-and-a-mini-meta puzzles lately. The team gets the mini-satisfaction of solving the minipuzzles, but by the time they're done solving the mini-meta, they also get the (deeper?) satisfaction that comes from solving something more substantial. (Those mini-ahas don't only come from mini-meta structures, of course. Figuring out one answer phrase in that cryptic crossword also yields that zing. But maybe the minis can have that one-phrase level zing, and a quick puzzle-level zing? Maybe?)
Anyhow, my opinions have changed over the years. No doubt they'll change more in the future. I dunno. How should one order the tough and not-so-tough puzzles?