I've seen webcomics with more dignified villains. I've seen children's cartoon shows with more complex antagonist characters (and no, I'm not counting ATLA in that).

I was once secret-santa'ed a printed copy of a webcomic in which a goblin has the opening line: "stupid humies!". This 'nightmare' dialogue is on the same level as that, and that was an intentionally stupid satire/parody, in which intentionally stupid characters has intentionally stupid dialogue.

The difference is, I doubt Paolini intended for this to be stupid.