Ah ha I see what you mean. Did some testing yes when they die they drop the crystal again, but you can't order them or give them a new orb. They don't die per se, but they might as well have died as they are in limbo as they can't do anything. You CAN use the infuse loyalty in them and they will follow you, but you can't make them stay in one place. It's just like any other pet what you invest into them is a one time thing. They die they die those resources are gone. So your options are make an army of them, just get a few strong ones and infuse everything they can take, or go with cats/wolves and infuse them to the max and keep blood samples of them to clone. The best way to clone cats/wolves is to start with 1 infusion get blood sample then infuse it again, get sample, rinse and repeat until you have a war beast. If one dies in the process start from the last sample collected and it starts with full health or give it victus between infusions to regen.
When fighting elementals I don't know if they shoot projectiles or not if they do you might what to go with ender hearth if it counts as an arrow.