Is Hex worth it at high levels?

[diplomancer]

Back on the original subject, I think hex having one or more invocations dedicated to improving it the same way eldritch blast does would not be remiss.

From earlier:
There is room for debate over whether it should have a prerequisite level, and/or shouldn't have the +1 slot level. The slot level increase basically moves the 8 hour duration from level 5 to level 3, and the 24 hour duration from level 9 down to level 7. I don't actually see the 24 duration as that big of an upgrade over the 8 hour duration, though I do see the upgrade to 8 hours as pretty big.

Other ideas:

Hexagram
Prerequisite: must know hex.
When you cast hex from a level 1 spell slot, you may target one additional creature. For each spell slot above level 1, you may target one more creature with the spell, to a maximum of six (when cast from a fifth level spell slot). Each creature has the same curse and therefore the same affected ability.

Cursed Blade's Hex
Prerequisite: must know hex; must have Pact of the Blade
Once on each of your turns when you hit a creature with your Pact Blade, you may cast hex on that creature without spending an action. If you are already concentrating on a casting of hex, you may transfer the curse to the creature stricken by your blade without an action, even if the previous victim of the curse is not yet reduced to 0 hp. In either case, the curse is inflicted before damage is rolled for the attack that triggered it.

Bottomless Spite
Prerequisite: must know hex; must be at least 9th level
When you cast hex, you may choose to do so without expending a spell slot. It is not upcast if cast in this fashion.

When considering new invocations, one must be careful not to make it basically a tax. I believe the Evil Eye invocation falls in this category, even without the upcasting. The next two (Hexagram and Cursed Blade's Hex) are fine. As to the Bottomless Spite, do you mean allowing Hex to be cast At Will? Sounds a bit strong, specially when combined with the Evil Eye invocation.

Also, don't forget munchkins and eye patches, sunglasses, etc...:p probably also best to make it clear that the eye transformation cannot be hid by a Disguise Self spell.