None of the options, as the Spike grenade is pretty powerful in PvP for Defenders. Sure it has a short duration, but its cone can hit half a team or more if you set it up properly during an engagement. That and it causes mass panic when their shields are popped in a bath of light, giving you time to kill the stragglers smart enough to get out of the rays. Edit: Its lack of use is simply just the meta copping out for burn and forget grenades, as I personally find a well placed spike grenade to be nearly impossible to escape without abandoning your objective. Like a land mine in a sense.