The way you guys sometimes communicate is truly baffling. One wouldn't even know that there was an event going on - there was barely any info at all. And when one did notice something was up, one wouldn't even know what in the Emperor's name was happening. And when one did figure out what in the Emperor's name was happening, one wouldn't even know how much of it was happening, where it was happening and how much was still left to happen before the heresy was thoroughly stomped out.
Is the end-event survey the right time to learn of a special boss fight? Tell us honestly, is this how you want the players to find out that you designed a new boss encounter? In a post-event survey?
It was bad enough that the Unsavoury Business "event" was barely more than an extra pop-up window with flavour text, when I only occasionally noticed an added enemy type at what seemed like completely random points (with zero way to track any progress) and that the rewards were indistinguishable from standard challenge rewards (at least once I was trying to figure out which challenge I had just completed only to realise the rewards were for a stage in this "event").
You want to make a mysterious event, that's fine. But I would suggest the following:
- Design an actual event - instead of simply adding a counter to mission mobs and calling it an "event";
- Let people know something is going on, what it is more or less about, what needs to be done (broad picture, I don't mean the details - anything is better than four lines in a Steam update post);
- Let people know exactly where they are at any moment in their event progress;
- If you add a special boss fight, it would be good to actually inform the players at the beginning of the event that something out of the ordinary grind is part of the event. Especially in case of this kind of non-event - many people won't even bother with the event if it's just a counter tracking villain and elite kills.
And if you really want to design a mysterious hunt in an online game, try to get your inspiration from games like The Secret World and its investigation missions, to see how to do it properly.