I -think- if a boss on a writ dies to these things, it doesn't register as you the caster killing them. I would try to duplicate it, but at my level it takes me a while to get through a dungeon and if the only thing hitting the bosses I fight are tentacles well...I'm going to loose

. Either way, last night I had beaten Manfred and there was nothing in my combat log about him dying, and no body left behind. The no body thing tells me the tentacles also kill remains, which is also true of shadow bolt by the way as well as likely shadow storm (though it makes a little more sense with that).
Anyways, I know this is incomplete but as I explained it would be hard to duplicate. I know shadowbolt for sure destroys remains though.