I can understand the argument on not spending development time on content few people will enjoy. Every piece of new content is a gamble. How many resources should be spent on it? How many players will actually make use of it?

The much maligned Lords of Verminion is a good example of this. Players reacted positively to an April Fools joke about minion battles so I'm sure the devs thought an actual minion battle game would be popular. Unfortunately the mode flopped. It also still costs a little dev time each and every patch since every minion added to the game must be given stats and an ability for LoV.

Ultimate Coil on the other hand seems to have paid off so far. Many hardcore raiders that would otherwise have nothing to do for 3 months are progressing on it and the community in general is enjoying spectating another World First race. It's quite possible that the content will be forgotten in a month after the hard core have cleared and the mid core have given up. On the other hand it's possible it will live on as a challenge for raiders to attempt in the months between regular raid tiers to improve themselves.

A lot of the negativity likely stems from players feeling like this patch was light on new content for them. I admit, I'm in this camp as well. I enjoy the usual updates (story, 24 man, beast tribes, ect) but the more experimental content doesn't appeal to me. I'll never attempt Ultimate Coil. I'll never use the bard perform action. I likely won't touch Rival Wings (unless you can get a mount that plays Exponential Entropy from it >.>).
Even so, that doesn't mean the additions aren't good for the community as a whole. As we see here many are enjoying challenging or watching others challenge Ultimate Coil, maybe some roleplayers will get use out of Perform, maybe Rival Wings will be a hit for PVP fans.

At the end of the day a MMO community is a collection of minority interests. I'm sure lots of players don't care about things I like such as collecting TT cards so I do support the devs trying to develop content for a lot of different players.
I just wish Eureka hadn't been delayed so there would be a new addition to the more casual endgame as well.