Well I don't do pvp, so my opinion is based on pve. I loved the system as well when AOC came out, but playing as a HOX basically all my combos did their main damage to one side, and mobs always directed shields to this side after a few hits. And in group content it was irrelevant. So basically all the system did was reducing my damage and removing available keybindings. But I can see that it could be nice in pvp.
HoX is a different in gameplay from the melee classes because it has a lot of reliance on its transformation mechanic, which is needed due to the HoX's glass cannon-ness. In addition to the transformation, you also rely more on spells than the "real" melee classes. I comprehend your perspective, because HoXs are really more of a mage class. I'm not sure I can say it's a hybrid melee/mage (in terms of AoC mechanics) rather than it's a close-ranged spellcaster.
I can also understand your criticism that probably the HoX, as having a strong aspect of being close-ranged spellcaster, makes the directional buttons kinda tedious. Interestingly enough the Priest (Priestess?) of Mithra was much better as a "caster" in that their attacks were based on range, yet they could handle melee characters approaching well. Without a 5 directional keys. I think the Tempest of Set also.
So I think they just didn't design the HoX well. It wasn't a good sword-mage character. It was a mage that was relegated to close range attacks that did more damage than the other mages (I think). Having the complete 5-directional melee system doesn't fit with that design.
Now the true melee class are better and have distinctions. Guardians being very straightforward. Conquerors more of a group-based aura type. Barbarians' and Assassins' variety are more noticeable in PVP but still they were more glass-cannon-y (especially Barbarians) so that made gameplay distinct. But playing that "Dark Knight" class was very interesting, as a leech-type semi-tank. For those classes you didn't have a bunch of skills/spells that you needed to hotkey, you just had a few significant and distinct ones.
Bear Shaman though, bro. Interweaving between melee and healing, in the manner that you needed to do damage in order to heal, and stuffies like that. I want to say it was complex, but it's not really complex as much as it gives you just enough to do and those things had distinct variety, so that you have to pay attention.
HoX may also have had less combos (instead having more "mage spells," if that makes sense) than the "real" melee classes, which might be why it felt repetitive meleeing in PVE. NPC shield direction was more important (though still not high brow complex) for melee classes because shield direction would limit what combo you wanted to use, which meant a bit of improvisation. Less repetitive rotation.
Admittedly it's quite possible that the Bear Shaman class was significantly better/more complex than the other classes.
Also like I said I hate "classic" MMO combat (sadly because I've played such too much...) and I also subjectively enjoy action-y combat. So there is a bias there.
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I really hate how Tortage was such a bait and switch though. And I'm not talking about VA. Motherfuckers.