This sounds like a petty critique, but I do not understand the names of your blights - and they seem like they are intended to be a big thing in your system if you list all four on the character sheet. The key point is none of them appear to me to have either associations or mouthfeel.
If we take what feels as if they might have been inspiration we have the four Chaos gods from Warhammer. And just looking at the names tells me a lot about the associations of the four gods. The mouthfeel of Khorne is starting with the hard C - like Clang and the name itself is short and single-syllabled for a direct god. Nurgle meanwhile sounds like burble and is sort of glutinous for a Lord of Decay. The tz in "Tzeentch" on the other hand is a lightning zap followed by another break with the tch at the end; we've a tricksy god where things stop and change. And Slaanesh is softer, and all wide mouth sounds. And all of them are short names - Khorne is just a single syllable, while Nurgle and Slaanesh are two each. Tzeentch is stoppier and startier - but stands out because of it.
Meanwhile I'm nowhere near as sure how to pronounce the names of your blights. None of them are anywhere near as short as Khorne; the simplest would appear to be Culghairm "named so because of its association with disease, disgust, moral decay, pollution, and resignation." This would appear in domain to be pretty close to 'Nurgle' - but Nurgle is almost sloppy sounding - "ur-ul". The sort of sound you make if you neither fully open nor fully close your mouth. Meanwhile the opening of Culghairm starts with a nice crisp 'C' - and then it continues with tongue movements almost like the decadent 'Slaneesh' with the requirement for a dextrous tongue, at the top of your mouth and the sound forward on the l and at the bottom on the a.
And with "Ice", "Forest", "Swamp", and "Burning Wastes" I'm not seeing the thematic breakdown and oppositions for all it feels very Warhammery.
I don't think it's a petty critique. It's not what I expected people to bring up, but that doesn't make it any less useful.
The four Otherworldly Domains are themed around the range of human emotions. Their physical environments where themed after their emotional component, not the other way around. Tiranmairg corresponds to sorrow, Scaymlah to fear, Culghairm to disgust, and Adhlacad to Rage (happiness is reflected by Andulra). The "Woeful", "Gloaming", "Plagued", and "Blazing" elements of the names were just as important as the "Frosts", "Woods", "Mucks", and "Wastes" parts. I was worried that the thematic association would be too obvious (especially that I state the emotion they are themed after in the first sentence of each domain), but I must have overestimated how effectively an outside observer could have caught on to that.
I neglected to provide a pronunciation guide because all of the words pronounced exactly as they are spelled, with the exception of the "air" grouping that I thought people could catch on to quickly. People seldom ever explain the pronunciation for a word with phonetic spelling. I shouldn't have assumed it would make sense to others. I will mention that in the next draft of the Guidebook. Either way, that should let you in on how to say it.
With that pronunciation cleared up I hope that makes it a little clearer why the names are like they are. If you wouldn't mind, could you pronounce them like that and see how they sound. I know what I think the mental effects of their sounds are but I want to know what others would notice.
Also, just for some extra context, all of the names are based on Irish Gaelic words for concepts related to that domain. For example, "Scaymlah" comes from the Irish word for terror sometimes anglicized as "Sceimhle" (pronunciation isn't the same, but it's somewhat close). The Otherworld in DoS was already based off of Irish concepts of Tir Na Nog and similar Spirit Worlds, and the language itself has a naturally mysterious and magical ring to it, so I thought it would be best for the names to sound like they came from Gaelic.