Obi-Wan places such moral restrictions on himself in all of his fights, unless you can post a quote showing otherwise (which I'm on board with)
I have to assume these moral restrictions don't include setting Grievous' organs on fire - with a blaster no less. And considering the very violent manner in which he was dispatched, I doubt Kenobi has any reservations with piercing cyborg lungs, heart or performing a decapitation. Just a few options that probably aren't on the table against a former Jedi comrade. And one who hasn't committed any particular crime.
There's a very specific reason why I italised the word "people", when referring to the types of adversary Kenobi will restrain himself against. The difficulties he has fighting Hett - creating a specific opening so he can disarm him - aren't present against robot. Which may go to explain why hett lasted as long as he did. Kenobi also has no reservations against Maul, possibly none against Savage either.
Hett at least caused Obi-Wan serious issues and landed a hit on him.
Yes, but unlike the Magnagurd, Hett had an environmental advantage, as well as the leisure of fighting someone who's trying to spare his life, while not reciprocating the same moralistic goodwill.
Magnaguards are a dubious measuring stick, given that Fisto and Maul have both wrecked them very quickly as has TCW Anakin.
There may be a few in-universe reasons why this is, let's look at them before hand-waving Maganagaurds entirely. The first is that their programming doesn't respond well to unpredictability, and that Fisto and Maul wield styles characterised by that exact trait. The second reason is the possible improvement of Magnagaurds over time. Or that the ones guarding Grievous aboard the Invisible Hand are simply more "elite" than the one's facing Anakin in TCW. For one, they don't seem to get up after loosing their heads. From an out of universe prospective, if the argument is that Kenobi is jobbing against Grevious' bodyguards for plot reasons, he can certainly do the same facing Hett. Especially since we have an internal account of the battle, where it's clear that when Ben gets serious, the fight is over instantly.
And again, the point of this is A'Sharad went from this rather mediocre state to perfecting his combat technique" over a century, killing thousands of opponents, and having his powers "multiply" by his peak.
That's one [part of the point. The other part of the point is establishing how good Hett is before the power ups. Presuming he was already on Kenobi's level - but only a little bit worse - then the endeavours during his journey to becoming Darth Krayt could indeed put him ahead of Dooku... and by fair degree. However, I think that he's a Tier Seven against Kenobi. The experiences Krayt had after the fact may well have taken him into the tier-eight rubicon, but it still doesn't put him ahead of Tyranus. If beating a centuries worth of opponents - whom may not even be particularly great - was enough to put him ahead of Dooku, then I had better see you supporting Lord Scourge against The Count too. But for some reason I don't see that happening.
Having favourable comparions with Caedus and Luke
Well I have mentioned numerous times that I'm not familiar with Apocalypse. My basis for Krayt comes entirely from Legacy. So feel free to enlighten me.
Krayt was duel wielding in this scenario,
.... No he wasn't.
In any case, I'm not interested in entering a debate of semantics and mechanics when it's fairly clear that Krayt is superior to Cade in an obvious way.
We he? When i looked back at the panels of the fight, I see Cade still standing after Krayt attempt to dominate him conventionally - through TK and lightning. He was taken down, yes, but probably because Krayt's used Force power Cade never expected to be on the receiving end of.
He dulled his powers with drugs at the beginning of the series, but it's noted that his powers had increased remarkably as he got more experience under his belt. Talon notices a large difference by the end of the book.
And he probably spent the previous years of his life on drugs and not doing much to improve his skills. The point is that he's a several generations diluted Skywalker, with much less training than Anakin. I don't give him special commendations for beating what, Taalon and Nhil? Who are ultimately just two skilled acolytes from a relatively unknown faction of sith.