The problem hex has is that, like psi, anything within 32 blocks of you (or more with wisps/circles/sentinels) is under your influence, the time to activate (TTA) is zero, and there are no counterspell mechanics. All this combined means pvp will never work with hex, due to the inability to avoid a hex caster's attack.
One of the easier Solutions is to greatly reduce ambit, or have a specific spell-ambit, so hex casters might still acquire information about their surroundings, but are only allowed to affect a small area around them. This would also encourage the use of projectile wisps, which otherwise only have niche/aesthetic uses. Using blink to close the range gap would also become more common, because it would give you range within a tick/hex and let you leave again equally quickly. My proposal is to give the caster 6 blocks(a bit more than hand range) of range and the greater sentinel equal range. I propose both wisps to have an ambit of 3 blocks. (Also ambit being inclusive rather than exclusive would be nice, even if it's just to eliminate the feeling of being inefficiënt when sentinel walking)
Another idea is to increase TTA. This is more complex. You might propose the "main sequence" of a casting item should take one tick per pattern, but that would be easily circumvented with iota embedding or external storage, akin to the cad spell circle. Another idea is to limit all casting to only one or a very small amount of patterns per tick. I reckon one is far too slow, and a few would be a nightmare to time.
Also possible is to pass every meta-evaluation to the next tick. This also causes timing nightmares, and gives loop unrolling an even stranger role than the current meta-eval limit does. Finally there could be a limit of one spell per tick. This would seem to me to ruin one of the core engagements of hex, the ability to alter the state of your surroundings in an instant according to your desire. Overall I don't think TTA can be increased in a useful way without ruining the identity of hex casting.
A commonly thought of solution for hex pvp is counterspells. A spell that has you predict an action another will take and prevent it if it happens, ambit reduction effects, inability to be targeted by actions, etc.. My personal favourite is to keep invisible entities from showing up in zone distillations. This would give non-casters counterplay against casters, and lends motivation to the wonderfully crazy idea of Ray casting through every. single. block. just to make sure you'll find invisible intruders, or bombing an entire continent because you're sure there is someone there, you just can't see them.
In conclusion, I'm sorry for formatting this like a highschool essay.
Anyways,
My personal ideal would be the reduction of ambit, lack of zone distillations on Invisible players, and a method to disable the sentinels of others. Because then every offensive strategy of hex casting would get countermeasures. Projectile wisps can be impulsed, cyclic wisps can be put in blocks, sentinels could be banished, and players are vulnerable themselves. (And circles are stationary/vulnerable to breaking). Right now I don't know how exactly you should be able to banish another's sentinel, but maybe altering banish sentinel to banish other’s sentinels within your ambit would be a start.