We can get drops from recoil now unlike prior to EoC, but they changed it so that it doesn't count as an actual kill. This is the current problem with trying to recoil any slayer task, we can get the drops but it won't count as a kill. For like 2-3 weeks after EoC was Introduced there was a way to make kills count but they fixed that method and I don't believe anyone has found a way around it.
I did find that if you target a creature by casting a curse on it and have someone else kill it, it will count towards your slayer task and count as your kill. This principal may apply to diaries but I haven't tested that. You could try doing that to complete your task, just make sure you do 0 damage otherwise you'll gain the xp for the kill.
If that works, the only explanation as to why it isn't counting as a kill would be similar to how we had to do damage to a creature in order to get the kill to count for a quest, or have ASA do the damage for us. Creatures may drop loot 100% by whatever damage they receive, but unless you or someone else actually does damage it won't count as an actual kill.
Blackston is a Naabe.
11-Feb-2013 18:26:33