Alright, just for fun. 🙂
Jack himself says that Wyyrlok holds his own against Krayt Reborn. Yet Wyyrlok was still weaker than Vong Krayt, whose powers were "outshone" by Muur:
On Had Abbadon, in the Deep Core, Krayt confronted Skywalker a second time. But a third Force-user possessed powers that outshone them both. Karness Muur, an ancient Sith spirit, blasted Krayt with overpowering energy, sending him over a cliff to the rocks below. - Insider 113
Now ILS can do as much mental contortion that he wants to pretend that "has powers" really means the ability to summon rakghouls (even though that doesn't factor into the context stated in the next sentence at all) or light up Christmas trees, but the most obvious and reasonable interpretation is that Muur's Force powers are greater than Vong Krayt's, especially given:
But Emperor Krayt might no longer be the most powerful Sith lord in the galaxy. Will Cade and Celeste have another Sith to defeat... or join?
Ergo, Wyyrlok is weaker than even a weakened spirit Muur, and Krayt Reborn can't be too far above him given his struggles with him. Even a full powered Muur is far weaker than SF Malak, so by power chains he is fodder to someone on the tier of, say, Mace Windu. Even Ulic is a match for a pre-prime Exar, who was not long from being able to one-shot Nadd's spirit, so it's very difficult to believe that spirit Muur > Ulic = Exar Kun.
You might point to Krayt's battle with Abeloth, but we actually don't have solid proof of Krayt's claim that Reborn > Apocalypse, or context behind Krayt's performance (was he amped? etc.). He had been declining in power for decades and there's no reason to think he was suddenly back to full power again. Now you might say that this is straw grasping until one notices that Krayt's Apocalypse performance is vastly out of proportion to his performance in Legacy. If you buy ILS's interpretation of the fight, he would've oneshotted a sub-Muur level fighter (Wyyrlok) instead of struggling with him.
Furthermore, if you actually buy ILS's interpretation that Krayt was about equal to FotJ Luke, he would be disqualified from the match for being more powerful than Yoda. Instead, ILS has to arbitrarily split the difference by arguing that the conclusion of his own point doesn't actually work but somehow half works and he's just powerful enough to win but not powerful enough to violate the criteria. The problem here is that Mace Windu is basically the absolute strongest character you can get in this fight because by RotS he's only barely below Yoda (probably not at all with vaapad vs. dark siders factored in). So the chances that the calculation of Krayt's power just happens to fall between Mace and Yoda is incredibly small. Indeed, given that dark-sider-drawing Mace Windu can defeat Palpatine, it's very possible that no dark sider can fit the "above Mace but below Yoda" criteria.
We get the same issue with Shimrra. If Shimrra really is Luke tier, he's above Yoda and thus disqualified. If he's not, then where is he? Just exactly above Mace and below Yoda? How convenient. In reality though Shimrra fought a really, really tired Luke who had just gone through a literal army of thousands of Vong, each of which is a match for a good padawan. Bart tries to get around this by saying that Luke was still able to fight seven slayers. Uh...yeah...he does this before he fights Shimrra, so he'd be even more tired by then! Regardless, despite not contesting full-power Luke's abilities I kind of want to see Bart's case so I'll ask for it.
Not that it matters, because Shimrra may be resistant to direct TK but what happens when the ground underneath him caves under or he gets blasted away by 5,000 mph winds? We have Galen Marek, whose fighting style hinges on fantastical offensive Force applications. He's Shimrra's worst nightmare.
What can Galen Marek do? How about powering the hyperdrive of a corvette with Force lightning at the beginning of the story when he was ragdoll territory for Vader? How about bringing down an imperial star destroyer? Do you seriously think Shimrra is getting anywhere near him? Can Wyyrlok touch him in feats? No? Does he have any scaling? Oh? So now we're left with Krayt - when has he ever replicated TFU-tier feats?
That is all.