I don't see how that was your take-away from my suggestion. Xenohunters wouldn't be going after ores. My idea was that, If they were given a pickaxe, it would be so slow that teaming up with a miner would be the obvious method of getting around the asteroid. As for them killing Xenos instead of the miners, yeah, that would likely happen. But, again, they need to stick with the miner to get through the asteroid. In the interest of encouraging player interaction, I think it would be a fair trade-off.
But if that's not good enough, we could go a step further. We could introduce Xenos that require a combination of Xenohunter and Miner weapons/equipment to kill. For example, an armored Xeno that needs to have its armor dislodged by a Miner's kinetic accelerator before the Xenohunter's darts can be effective.