These “pets” are immortal as you say, so they never die and all agro goes to you anyway. Having a short leash makes them useful for melee only.
If you can use Pet Attack regardless of distance (almost), their short leash is useless and only frustrating the player - because one has to constantly use pet attack instead of using that button for other skills for example.
I believe a long leash such as other pets have in aggressive mode would be better.
And you could even make them long range aoe damage dealers, to fit the “guardian” role in the skill description. In that case you can have a shorter leash so they never leave your proximity. Similar to a crystal ball over your head that throws away multiple ice/fire/lightning etc. shards/bolts.
Would be more fun and functional.
What do you think could it work ?
I think that those two have a bit more leash, these guardians really stand there doing nothing while a horde of archers kills you. I would guess that most people use them for their aura with resist reduction, this doesn’t get applied in those situations.