That poor, lonely instance Oculus. Its looking for group channel is always dusty and vacant, its loot is scarcely touched. The bosses chill out with impunity, which is rather a difficult task to master (but they've had the time). The drakes have plenty of time to make more whelps. The empty holes in Glory of the Hero mock those looking for a group, even as their friends respond to their requests for help with whispered obscenities and PTSD-like symptoms.
So what is it about Oculus that inspires such horror and loathing?
The first could be the requirements for Heroic achievements. You'll need to go no less than three times, and perhaps more depending upon the lifespan of your drakes and if you can get from the first boss's dying throes to the last boss's dramatic collapse in under 20 minutes. Not a single boss in the instance besides the last has any achievement attached to it. And there is simply no way to get all the achievements done in less than three runs with the inclusion of Experienced Drake Rider (and your drake must be alive at the end of the fight to receive credit).
Another issue would be that this instance, at least on the final boss, relies heavily upon coordination and competency. It also requires adaptation and understanding of your mount's abilities. You have to have five people working together with an understanding of how to function in varying levels of various drakes, and it takes a lot of trial and error. Last night I was in a five Amber Drake group (to get Ruby Void and Emerald Void in one go) and though we eventually got the boss down, it took some coordination, failed strategies, and consultation with those who had done it before (thanks Aegus and Iliana). We rode our drakes naked so we didn't rack up too much of a repair bill, and tweaked our strategy until we had it. But even with experienced raiders along, there were deaths and adjustments until we got used to the strategy and our drakes.
I suppose the main reason people dislike Oculus ("dislike" being used in its most extreme form here) is that, no matter how geared you are, how far you have progressed, or how you spec, it won't matter for the final boss fight. Your Drake will never have more health than your party can buff it (at the expense of buffing their own Drake), your moves will never do more damage than they do, you will never heal for more than you do, you will never shield from more than you do, at the first moment you step into Oculus to your last run. The Drakes are an equalizer, so that a healer can DPS, a tank can heal and the DPS can tank. Your spec can be terrible, and you can ride a Drake and win.
In some ways this is good. While the first three bosses need some decent DPS, they are manageable with people under 2k. While not all the achievements can be completed with low DPS, many of them can because on Drakes it just doesn't matter. All that matters is that you understand how to use the Drake in coordination with the other people (and therefore that they understand how to use their Drake as well).
However, people dislike Oculus because they have no control over improving their Drake. They do not get to choose what their Drake can do past color, and sometimes not even then (due to group makeup requirements or achievement purposes). This lack of control is frustrating and puts a lot of people off. They do not like having to "learn a new class" while riding a Drake, because, for all intents and purposes, that's what you are doing. It's impossible to cover for someone; if the only Emerald Drake dies, then you're SOL where healing is concerned. No one can off-heal. This rigidity can be irritating.
I personally enjoy Oculus. The first three bosses are just complicated enough to require environmental awareness and precision, while not completely blocking you from the rest of the instance. Also, since your own gear does not affect your Drake's performance at all, you are free to remove the gear and eliminate a lot of the penalty for wiping. It's unique and fun to learn different strategies and Drakes, in my opinion, and I look forward to going back.