Have you thought about slowing down your storytelling? It doesn't work in novel format because you want to propel a reader, but in this Sunday comics type it may help deflate some of those balloons.
Another thing to try is taking your shears and cruelly chopping off any dialogue that isn't completely vital. Let's take that first balloon in the comic you linked: "It wasn't just the weed. All the stuff from the shootout was missing. Shells, jewelry, photos, clothing, you name it."
Would it be possible to keep the same impact if it was something like: "Not just the weed. Everything was gone. Shells, jewelry, photos, you name it."
You might be able to chop it more, but I'm sure you get the idea. It's tough chopping dialogue, especially if you're a student to the way people actually talk. Problem is, dialogue can't be real speech without being mostly mundane ("Um, uh, so like, uh, the weather is pretty like, uh, nice right now, right?"). Start off with adverbs, adjectives and other emphasizing words. That "actually" in the second panel is taking up a lot of space and not giving much back.
I like that punchline, though. And is she freaking spitting in his beer? XD