Where did you find proof of this? Does the second "corruption" supersede the first one? Does the minion gain abilities of both dragons but only listen to one? Interesting combinations for future expansions if so.
Crucible of Eternity - both story and explorable - holds creatures influenced by multiple dragons. Sadly, we don't know their mental state, though Kudu, when he intentionally became corrupted by multiple dragons' magic, retained his personality (I suspect this is where the Nightmare Husks present in the Crucible of Eternity come into play - the Inquest studying, and managing to duplicate on a mental scale, the sylvari's immunity to draconic energies).
We don't see any two ED minion groups near each other outside the Crucible of Eternity though, as the only one which can be close to other minions would be destroyers, and the closest those come to any other dragon minion force is in Mount Maelstrom.
I think that the Nightmare Court aren't akin to Cadeyrn's original view on life is the whole point behind what the Nightmare does to sylvari. This is shown in the last sequence of the short stories from the blog post - how Cadeyrn goes from "I will be heard by the Pale Tree" to "we shall rule Tyria and elapse all in nightmare." Hence the whole "there's no return" concept tossed at our face several times - it's not that dissimilar to humans having traumatic experiences and being unable to overcome them. Sure, it's possible, but it's oh so easy to fall into a relapse and you're going to be scarred psychologically for life irregardless.
What corrupted Faolain was the Nightmare - the darker side of the Dream of Dreams, in effect, evil and what the Nightmare Court is seeking (via claim or not) to bring to the entire sylvari race.
It's hinted, if I recall correctly, that Faolain first got touched by the Nightmare when she and Caithe encountered Zhaitan for the first time - or some other horror of Orr (I just recall it talking about being from their first trip to Orr) and from there it uses the whole cliche of "if you look into the abyss long enough, the abyss looks into you" where Faolain "looked too long" and Caithe didn't.
Kralkatorix has nested in the Crystal Desert. I suppose there probably are artifacts from the ancient Elonians still, but his branded don't seem to move out of the branded areas (for all we know) so I would assume his supply is limited.
The branded are moving south and east - threatening to leave the Dragonbrand in Fields of Ruin (at the very least).
But I would agree that the Elder Dragons feed differently. Just as they corrupt differently I think they sustain themselves differently - but in the end it's all "energy" and not consumed via food. Heat produces energy so there's Primordus; Jormag's all about mental corruption so there's probably something there just as Zhaitan's about magical radiation for his corruption, and Kralkatorrik seems to corrupt physically so... I am not sure where the energy comes from there.
Some numbskull stole a seed then planted it while daddy was asleep, giving birth to a Lieutenant with no general. Desperate for some form of guidance, this Pale Tree took on the teachings of Ventari and created the grove we now know.
Explain Malyck then.
'but no other minions show signs of free will!' In one of the later missions, you meet a minion of Zhaitan who Trea claims 'is not enslaved...'. The minion responds that he obeys because he chooses to. Lieutenants CAN have free will; the dragon might be imposing a will. With Grove Daddy still asleep, Pale Tree developed this free will. With so many Sylvari, I doubt he could enslave them again.
Free will in the minions is dependent upon the amount of magic fed back into the minion - more magic, the stronger and more intelligent the minion is, and the more self awareness it has. Though all minions are fanatic servants to their dragon, irregardless (I'm unsure of what minion you're referring to that's said to be not enslaved, however).
'But CoE proves minions can be dual-corrupted!'
That's one interpretation. Another is that if you corrupted something with multiple sources AT THE SAME TIME it would gain multiple corruptions. Also worth noting these things don't obey the hive mind of their corrupted brethren (unless I missed Alpha yelling 'for Zhaitan!').
Kudu's Monster disproves this. It is a risen giant without a doubt, which has been given the abilities (read: draconic energies, which is the source of corruption) of Kralkatorrik, Primordus, and Jormag as well.
'But they have no free will!'
As stated above, if the dragon is defeated *cough* then the lesser beings MIGHT be able to gather some form of free will. this would create two player races that people would love to get their hands on, and the 'limited' races of the game being so... limited.
Actually, at the end of the personal story, the cinematic that plays says that the risen are still acting the same, if I recall correctly, and even if I don't recall correctly, the Arah explorable dungeon has dragon minions with the same personality system as before Zhaitan's death - powerful ones have more self awareness and intelligence than the weaker ones, which are just as mindless zergers as ever.
Sylvari being minions that escaped control gives them the background and presence to flush out some of ANet's promises, and sets the stage for some really neat interactions later. It also fills in several gaps, and despite reading this entire thread I've not seen any great arguments against it.
In reading this entire thread, I have not seen any great arguments for
it either. You're missing a lot in your post which works against you.
My idea claims that minions have free will by default, and the dragon exerts his will over them, removing that.
No, actually, it's the opposite - the Elder Dragon does indeed take the free will, when the creature is corrupted, but once a minion it will not have free will unless the dragon allows it.
Though "free will" being used is a misnomer because it's not really free will but self-awareness. The minions who are more aware and intelligent will still never, nor can they I presume, betray their Elder Dragon. The only reason Glint was able to escape Kralkatorrik's control was due to the forgotten having found a means to reverse the Elder Dragon's corruption - well, non-physical corruption.
Since we don't have any confirmation on where the seed for Malyck's tree came from, I can't say much on it except that if it was planted without the influence of the sixth dragon it makes perfect sense they to would free will. Since they have free will they're not 'mandatory evil', but they also don't have the tablet to guide their way. They don't rebel against a teaching that was never given (like the NC), but I do admit the strangeness of him not being in the dream.
That is one huge of a damn big stretch there bucko, especially given one of your backings is wrong.