@Leo80221 While I agree that the manga doesn't show well the scale of the army's numbers, Megiddo is however exactly how it was in the novel. Also, no, the rays aren't "solid objects." They are described by Razen as physical in nature in the sense that they aren't magical, that they are a natural phenomenon that's been manipulated. Also, this method of redirecting the light rays with the droplets is there so that every ray goes through more than one person.
As for Razen's theory of each not being able to go through more than two people, it's just his theory and it doesn't take into consideration several things (such as how the rays can just arrive from above or that they can just be redirected around the shields). It's likely that it isn't as simple as he makes it out to be. Furthermore, the rays being actual concentrated light, it would make sense for them to dissipate after some time and after going through a certain amount of matter. It's already good that they can act like lazers going through a few people each when they are just natural concentrated light. Plus, considering that Rimuru can continue shooting countless amount of such rays, it's not really a problem.
Now, back to how the army's scale was depicted, I believe it would've shown how numerous they were much better if we had gotten a better bird's-eye view of the army from Rimuru's point of view in the sky rather than just from 3 different locations within the span of terrain was occupied by the army (1 last last chapter, another in the .5 chapter, and the zone where the King's tent was this chapter).
"Merciless" still affected the rest of the army and killed several thousands (likely close to 10'000) even if Rimuru wasn't physically present near them. It also affected the fleeing solders. The ones where the king was were prostrating themselves, going along with what the king was saying, hoping that it would contribute to them not dying. However, those, the ones fleeing in the other parts of the army(which were ALL under attack by Megiddo at the same time) and those on the ground who were somehow still alive (for the ones who weren't struck with the rays in a spot that immediately killed them) all died from "Merciless."
Sure, the scale of the army was depicted well, but that doesn't mean it's not implied to have still been of that scale.
@Fenrir00 See this comment for why it isn't some "hard light" in this case either.
Also this comment for how Megiddo works: https://mangadex.org/thread/199520/5/#post_1460643
