I'm a fan, and remember that timeless classic well. Kudos to Harlan Ellison for injecting humor in an absolutely serious episode. But as you pointed out, that's entirely the writer's choice.

Harlan Ellison didn't write any humor into "City on the Edge of Forever". I don't see anything funny about a down-and-out guy accidentally killing himself because he stole McCoy's hand phaser.
Actually, there's a lot of "City" that Ellison didn't write. That episode is notorious for the behind-the-scenes rancor between Ellison and Roddenberry, and in fact Harlan Ellison dined out for the rest of his life on how Gene Roddenberry and the other executives at Star Trek "ruined" his script.
I've read Ellison's original script (it was published in a dramatic anthology called Six Science Fiction Plays). It wasn't a bad story, but it wasn't true to Roddenberry's Star Trek. He had drug-dealing happening on the ship, and there was too much mysticism going on.
Both versions won writing awards, so it appears that people saw merits in each.
It's been over 20 years since I last watched Babylon 5, and am blanking on who the Vorlons were.Consider: if a sufficiently more advanced species wanted to keep tabs on us - let's say, like the Vorlons from Babylon 5 -, would they send field teams or simply intercept our own satellite system?