Yeah, I think I might have been guilded with you when SoD got taken down on Phinny. Like 90% sure of it. I remember this discussion in /gu about how Brekt just kinda fucks off after the fight and there's nothing else. It's definitely kinda lame after everything before that.
The Discord stuff is left (intentionally I hope) vague in general. What is Korafax, their home planet or a weird space-tree? Dunno. Is Kuua their home planet or just a world they conquered? Dunno. I don't think we've seen their homeworld because I don't think they have one. They just expand through the cosmos, taking on different forms as a legion (absorbing conquered races) as they continue to weave their way outward. They're an amorphous mass of destruction that lacks order, whether a home territory or a clear leader. The closest we can get to a "source" of the Discordlings is the thing about generals being spearheads for discord as a concept, or whatever it was.
I'm not sure if Brekt was intended to be Mata's boss or Mata's equal, head of a separate wing of Discordlings. 90% it was the latter, but I'm given pause by Event 6 in Citadel of the Worldslayer being called "Overlord Muram" on the lockout screen. There's no Overlord Muram in the actual event, but you fight (reanimated corpses of?) a bunch of bosses from GoD and OoW in rapid succession before continuing onto Brekt. I have a suspicion that the original idea there was to have Overlord Mata Muram himself be the last of these reconstituted bosses right before Brekt, hence the name of the event, but the idea was dropped during development. If that had been the case, then it'd clearly position Brekt as being above Mata in the chain of command. However since the Overlord doesn't actually appear, it makes more sense to the lore to have them be equal and separate generals.
With Tunat merely a minion of Mata, I think it's safe to say that there are two more Discord overlords out there that could be utilized in the future. It would be great to get that level of science fiction again in EQ, dropping us on a new world etc. And maybe we could get some answers as to the nature of Discord.
There's also something in the lore about the "Alabaster Tower" and "The Thing's Eye" making themselves apparent during the final battle with Discord, but I have no idea whatsoever what those are referring to, if they're something that happened already and I missed it, or if they're part of scrapped story ideas that don't mean anything. Maybe The Thing's Eye is the core of Discord that controls the four generals. I don't know. I just know I'd really like to see more done with this concept. The Luclin remake actually looking good, the 64 bit enhancement, and the devs seemingly having a lot more money/resources to work with going forward have given me some high hopes that future EQ expansions will be worth sticking around for.