4e provided the ravaasta in Manual of the Planes, which are not-quite-arcanaloths that seem to have been specifically designed to comfortably fit into the A'Kin and Shemeshka roles of plotting fiend-types that you're more likely to encounter in a social context.
I like most of the Yugoloths as individual monsters, though i'm perfectly fine with them not being a specific category. I very much like the categorization of them as mercenaries. I mean as fiends go they're no where near as boring as like.. well basically the entire grouping of Devils.
There's a 3rd-party book by Blackdirge that adds "daemons" to 4e: https://www.drivethrurpg.com/m/product/62298. It does a really good job of giving them a history that ties into the 4e cosmology, and a power set that feels kind of like the demon "variable resistance" but different.
I've never thought of mezzodaemons as being particularly bug-like, but that's because my mental image of them is Russ Heath's Fiend Folio illo, which makes them look more like a chitin-y pit fiend with a bat head.
Yes, yes I do... Man... I think I lost twice the Internet points I've ever had...
More on the Mezzodemons (to try and obfuscate my earlier blunder) - I've had great success in using them as super-sticky bastards. If you can get one of them to the back row and skewer the leader, watching all the party converge on it just in time for it's breath attack is a thing of beauty. :evilgrin: