Collector's Bounty buff not (properly) working in raid groups?

This weekend me and a couple of friends (3-7) man ran Sepulcher for hours to try get the Zereth Oversee mount, we didn’t see any drop. Even with a 5% drop rate we should have probably seen any drop.
Looking around on forums I’ve been reading from people with same issues, or with Vengeance. So I’m just wondering if there is an issue, or is this intended not to work, or is this just really bad rng for everyone.
We have planned more runs next week, since most of us can solo this content on most toons, and would be such a waste of time if there was an issue. Bad rng we can live with.

95% chance not to drop…

I don’t want to be rude but you and other people starting conversation about it on forum must understand that this event gives you higher chance, not guaranteed chance for mount drop. Can be even situation when you don’t get few mounts during event because of your bad luck. What I noticed personally this buff definitelly works. I got SIX mounts which have 1% drop chance in 3 days. From other side, few mounts I still didn’t get. I did runs on all characters and I wait for next reset to try again. But buff is 100% working.

I see you finally understand what “5% chance” means … I’ll point it again for you … CHANCE

Just because you and your friends enter the raid and defeats the boss, doesn’t mean you’re guaranteed for it to drop. You all roll the dice of the RNG system. Next week you’ll do it again and maybe 1 of you will get the mount.

The following week, 3 of you will get the mount. The week after that, maybe no one gets it.

There is no bug or problem with the system. Just because you don’t receive a mount, when the drop chance has been increased for a month, doesn’t mean the “buff” is not working properly. It’s working perfectly fine, you and your friends were just unlucky.

If you have alts, log onto those and try it again. This is the beauty with such a fast clear of the old raid content. You don’t need to spend hours going through 1 raid on 1 character. In the space of an hour, you could clear Sanctum 7 or 8 times with your alts.

So if you don’t success try, try again!

yeah I also made a post about this. I even asked people who were doing 60+ runs on alts on relatively full raid groups. They said most runs had no mount drops and just a few had one drop.
Personally I think even with the buff still being this low, it should’ve been more visible in these raid groups. More mounts should’ve dropped than what’s the case now. So yes I do feel like there’s something going on with raid groups as well.