Hex as a skill is broken and has been broken since TFT release. Hexing a hero prevents them from gaining experience points. This is not intended behavior, nothing in Hex’s skill description says it should be doing this.
I really don’t think anything in this game should prevent a hero from gaining experience points that they should have otherwise earned. It even screws over a secondary hero, so if you have two of your heros side by side, and one gets hexed as the enemy Blademaster is about to die for example, your second hero gets halved experience points like what you should expect to happen when two heroes are close to each other, but the hexed hero still gets nothing. Further sapping away more experience from the second hero for no reason. Even if this was how Hex was intended to behave (preventing a hero from gaining experience) at the very least it’s still bugged, they should make it so your secondary hero receives full experience while the hexed hero receives nothing. IMO this is the worst bug currently still in Warcraft 3 as a whole and I surely think effort should be put towards fixing it or at the very least fixing the second hero receiving halved experience points when it should receive full experience points and updating the skill description to inform of this effect.
I also don’t think this should be like one of those SC1 legacy bugs that shouldn’t be touched just for the sake of it.