What you were expecting to happen, and what actually happened:
Expected the Dragon Eggs obtained to follow what was indicated in the weekly event page.
Dragon Eggs obtained vary wildly, the following is a sample of 6 Crossbow Tower fights including the latest as shown in my screenshot: 9,11,18,20,15,25.
I am not sure as I only noticed this later but I believe the first fight at lvl 10 does give the stated amount.
How often does this happen? When did it begin happening?
Every fight past the first lvl 10 fight.
Steps to make it happen again
Initiate and conclude any fight in the Dragons’ Defense event past the initial lvl 10 fight.
I’ll crunch mine when I get back home and start playing in the evening, but so far I tend to side with @Fourdottwoone - if I recall correctly, there already was an event with increasing points and average 1.18 multiplier.
First I was taken aback by the score needed per member (13033.33…), than I recognized the scoring is strange.
Last 3 crossbow tower I remember yielded 30 33 18, I have no idea what is the formula.
I agree, it´s getting harder and harder every week to find some motivation for the game. Again, another week with a significant bug (missing campaign task) and the scoring for world event is completely weird and isn´t explained in the official news post. No word about an increase by the number of fights or a random multiplier at all
adding my stats because I heard people in guild talking so kept track. I bought up to the weapon (tier 4) and took a few lower for scientific purposes, but mainly the higher option. I still got outscored by a guild mate or two by over 1000, so it almost seems immaterial what you choose, just how lucky you get on the random drops. One guildee who bought to tier 5 said they had a 71 egg drop…
4 people at tier 5 had scores of 10,160 to 10,580 so far. looks like 10 of us at tier 4 (although a few may have sigs left, not 100% sure) and the top 5 are 7,400, 7,250, 6,910, 6,550 and me at 6,140. then 6,070, 5,940, 5,850, 5,760, 5,500.
also, i think (but can’t confirm if devs don’t answer) that it’s not bugged, the description is just incorrect. it scales, plus has random drops.