Pretty straightforward, I was playing Orks today and actually had 2 grenades so I decided to lighten the Servo Skull spam. Except it didn't die. Maybe it was a bug, but it sure seemed like I dropped the grenade in the right spot. Yet it seems to me that in addition to it's other advantages, frag grenades don't hurt it. Say what you will about whether you think it's okay for a piece of warhear to have better TTK than support classes of other factions, that there's a strong argument that it's better than channeling and doesn't make you a sitting duck to use, but it definitely should not be grenade proof. That's ridiculous.