Thrall
Tier: Yes, small city level. That's what Thrall's showings put him at. If we assume that Jaina's wave did indeed have city-level amount of energy, even though we don't really have a calc to substantiate that, then the scaling actually fits quite well as he was only
barely holding it off whilst pouring all of his strength into trying to stop it.
As for 6-C, Thrall has no island level showings. Especially not in Legion where he had
already lost his shamanic powers. All in all, you're giving him a bunch of unnecessary keys that he doesn't need. He might have been weaker before cata/mop (when he peaked), but by an indeterminate amount and even then, probably not by much.
Dragon Soul: Thrall's use of the Dragon Soul wouldn't even qualify as optional equipment for him, let alone anything else. It was a one-off thing that he got to fire off a couple of times, nothing more. There's absolutely no reason for a Dragon Soul key.
Speed: Scaling to Illidan is fine-ish... Though it would be downscaling more than anything else.
Healing: Thrall hasn't shown any higher aptitude for healing than average shamans. Also, Healing isn't measured under the same metric that's used for Regeneration.
Mind/Fear Resistance: Game mechanics. It's there to prevent raids from cheesing boss fights by stun-locking entire phases out of a fight. Many boss characters appear in Warcraft 3 and the only CC that I remember them being immune to back then was a Banshee's possession and Polymorph.
Arthas
Comparing paladin Arthas to Thrall should be fine but nothing after that. Once he becomes a Death Knight he gains new powerful hax abilities, but he isn't portrayed as having become ridiculously stronger than he already was before. The tier "6-C" pops up again here for some unexplained reason. I assume that these are comparisons to the Elemental Lords, but quite frankly none of the characters mentioned here have anything to do with them.
One shot Uther the Lightbringer
No he didn't. It took a
good dozen hits or so to fell Uther, and that was only after a very hard-fought fight.
High-6B: In no way, at any point, is Arthas portrayed as being more powerful than the weakened Yog in Ulduar, let alone Malygos. He has obviously grown stronger by becoming the Lich King again, and has certainly gained ever more powerful new abilities on top of having full control of the Scourge, but he is still affected by the exact same things that he already was before he became the Lich King. Namely, Sylvanas/Jaina in the Halls of Reflection. Hell, a well equipped DK like Trag can
damage Arthas too. Even the writers were of the opinion that Arthas wasn't a particularly strong fighter himself, and that someone of Lei Shen's caliber could take him.
Type 6 Immo: Did you actually bother to read the Immortality page? Specifically the Type 6 entry? It pretty much describes the way in which the Helm of Domination functions.
Resistances: Game mechanics. Arthas is the perfect example of that. In the Halls of Reflection dungeon Sylvanas dazes arthas, and Jaina freezes him in place on the Alliance side. Obviously, doing this to him during his boss fight is not possible.
Stamina: No they don't have this by default. A claim like that will require some serious proof.
Dragon Aspects
CC resitance: Same as above
Malygos intelligence: Mentally unstable would logically belong under "Weaknesses", but you are correct that he has largely recovered by the time of his death.
Lifting Strength: Class 25 is a bit low, Dragon Aspects are insanely huge. Class T however, is too high, Deathwing has never outright lifted any mountain.
Galakrond
This profile is terrible, It should honestly be considered for deletion.
Flight: I can't tell if you're saying that in jest or not. Galakrond flies from the start of his book, through the middle of it when he is at his largest, and all the way up until the moment of his death at its' very end.
Lifting Strength: Class M is fine, maybe even class G. Class T is probably a no, though. Certainly not for Deathwing's reasons as stated above. It's hard to say for Galakrond however.
Kel'Thuzad
Tier: Same as for Arhas' Death Knight key. 6-C is completely out of place.
CC Resistance: Again, as before.
Tirion
Tier: Since LK isn't really High 6-B, then neither is Tirion.
Stamina: What long battles? How long were they? Withstanding torture is more of a willpower feat than a stamina feat.
Intelligence: No, no he doesn't. Above Average is where he's at.
Bolvar Tier: I guess he didn't roll over after a single shot from suped up Sylvanas, that's gotta count for something at least a little. But since Arthas isn't comparable to the Dragon Aspects...
Titans/Void Lord Tier: Probably for whatever reasons are listed on their profiles.
Old Gods
Stamina: They waged constant war with one another, but these wars aren't anywhere near well enough described for you to make the statement that they didn't have space for downtime. They could have very much had the opportunity to rest. Same thing for being "active" after their imprisonment.
Poison Manipulation. Only Yog has Poison manip and it's because he uses a poison spell during his boss fight.
Time Manipulation Resistance: I can't remember ever hearing anything about them being unaffected by the Emerald Dream in the manner that you're describing.
Nathanos is fine except for all the things that I've already mentioned above.
All the other things that I didn't address are fine by me.