Hex needs to be cast within 90ft of its target and has Verbal components. Its target is going to know immediately when its effect hits, but even the people near them are going to notice unless they are in a noisy area.ASSASSINATE
Starting at 3rd level, you are at your deadliest when you get the drop on your enemies. You have advantage on attack rolls against any creature that hasn't taken a turn in the combat yet. In addition, any hit you score against a creature that is surprised is a critical hit. Hex is cast before combat starts usually, it does have a 1 hour duration after all.
Surprise: If you’re surprised, you can’t move or take an action on your first turn of the combat, and you can’t take a reaction until that turn ends. (We have been interpreting that to mean your surprised until your initiative comes around .. Guessing thats not right ?)
... This is quite practical but in my head I can only think of it like a mum attaching a child's mittens with elastic so they don't lose them.
Hex is a Duration 1 hour spell - Concentration. Yes has a range of 90 feet. But says "If taget drops to 0 hps before this spell ends, can use a bonus action to curse a new creature".. So cast spell.. 20 mins later meets some creatures.. uses bonus action to curse a target.
I also don't see why you can't fire a second one with your BA. You can't use them next turn, they're not loaded. But that first turn seems right.
Flamestrike is correct: the game was errataed in such a way to completely hose dual wielding hand crossbow users.
On the other hand, no balance is lost by simply saying yes to the player: "yes, you can use two hand crossbows, that sounds awesome".
Or "no my campaign is not a John Woo movie."