Is Hex worth it at high levels?

[diplomancer]

I am not sure you and I use "tax" the same way. I am going to explain my understanding of it, and ask you to either give me yours and how it's different, or explain how these qualify as a "tax" by the definition I'm going to give, as I am not sure I see it. Thus, I am not sure I see the problem you mean to highlight with that term.

To me, a "tax" is a thing that every member of a particular class or subclass is required to take to actually function the way it's supposed to function. One could make an argument that Hexblade Patron is a tax on Pact of the Blade, if one believes that Pact of the Blade was underpowered enough that it couldn't function properly before Hexblade existed, and needs Hexblade now in order to work.

I have seen arguments that eldritch blast is essentially a tax on all Warlocks, since no Warlock should be without it and it is inherent to functioning "properly." I am not sure I agree, since it is nice, but not that much nicer than firebolt without its invocations enhancing it. Perhaps one might argue that eldritch blast is a tax on those invocations, and the invocations should give them.

So the only way that I think these could be a "tax" is if hex is, like Pact of the Blade, so underpowered that it is probably not worth taking on its own. Even then, these become a tax on hex, itself.

I have seen people argue for picking up hex with Shadow Touched or Fey Touched, so I am not sure it is entirely that weak. Thus, I am unsure how these qualify as a "tax."

I may, again, not be using "tax" the same way you are, and am interested in hearing what you do mean, though.

I mean that almost every Warlock will feel the need to take it, by level 5 at the latest (by level 3 if it has the upcast feature). It's a straight- and significant- damage increase, kinda like Agonizing Blast (which is also considered by many a tax on Eldritch Blast builds, except this one applies both to Eldritch Blast Warlocks and Pact of the Blade Warlocks equally).

It's like the new Warlock they tried to sell, where Mystic Arcanums became invocations... but what invocation is going to compete with a 6th level- let alone a 9th level- spell?