I had this problem yesterday: killed 3 bosses, got 1 skull. The first time I wasn't using the buff because I'd misunderstood the announcement and thought I didn't need it. The second time I got the skull and the 3rd time I didn't even though the buff was active, but I think that's because I didn't do enough damage - I came into the fight late and was on my crafter who doesn't do much damage anyway.

The 3rd time I didn't get any loot, even the normal boss drops, which is why I think it was me not doing enough damage for credit rather than a problem with skulls. But I saw other people saying they weren't getting skulls, and I'm not sure how much of that was due to not using the buff or other problems and how much was them not dropping when they should. I'm going to keep looking out for patterns though.

Although I doubt ZOS will consider it worth fixing for such a short event, unless it's stopping large numbers of people from getting any skulls at all. More likely if there is a problem it will be fixed for next year.

There's probably still a cooldown between skull drops.
That's how it always worked so don't collect them too fast.

Pretty sure there might be an add-on for it too.
Edit:
If you're on PC, it's available here:
https://www.esoui.com/downloads/info1501-PlunderSkullTimer2017WitchesFestival.html
Alternatively, search for it on Minion.

You have to be in the top 12 damage dealers to get a boss drop. Last year there was a cooldown too so assume it's the same this year. Cooldown on individual bosses was 5 minutes and only two in a five minute period, so if you get two bosses a minute apart you wouldn't get another for 4 minutes.

I got four dremora and five normal but on some quest and delve bosses they just were not dropping at all, even when I was the only person killing them and plenty of time between.

The dolmen ones I can understand as if you're low level there are so many higher level, high DPS there that you don't stand a chance. I got one dremora and one normal from a dozen or so dolmens in Auridon (PC:EU), it was so hectic.

Mind you I did get lots of jewelry to decon

Lightspeedflashb14_ESO wrote: »

There is a cool down, pretty sure it is 3 minutes, if you kill a boss in that time you do not get a skull.

Yes, there is a 3 minute cooldown.

I've had this, although the funny thing is I was doing some dolmens today and on 2 of them there was more then 1 boss and i got 2 skulls drop from both dolmens, go figure