The current situation is that if a player is killed before the henchman, they are dismissed and automatically return to their spawn location. This is great!
However, if a henchman falls in battle before the player, they are killed outright and won't be available again at all until the next reset. This punishes other players who might wish to take on that henchman.
With the great abundance of boss-NPCs that lense out mid-combat on the server it seems only sensible that henchman have picked up a trick or two to prevent them from dying. Have them lense, jump away, slink into the shadow, or just yell out "I must retreat" and disappear. The character responsible for their retreat could still be unable to renew their contract until the next reset, but at least this way the henchmen would be more often available and you would have to have less suspension of disbelief when you find them again after rifling through their remains for treasure the day before.