I wouldn't say the trial is "too hard." However, I do have two suggestions that I think would be useful.
First, since there's no tradition way to wipe (unless the dragon reaches the end), there should be an option to "vote restart." Even after a couple runs it's pretty apparent that if the dragon reaches a certain point, with a certain amount of health, there's really no chance of winning. There's very little point to waste those precious minutes watching the dragon go through with the inevitable. I think that time could be much better spent coordinating the group.
On that note, should the timer expire, I think that there should be an option to restart the instance with the same DF group (if the members of that DF group choose to, of course). Coordinating a group of new people is almost as time consuming as the fight itself. I had one DF group, last night, that was learning the fight rather well. We were making steady progress, with each attempt. We would have actually won the fight, if we actually had ten more seconds to spare (seriously, ten seconds). Of course, the timer expired, and we were kicked from the instance. The group dynamic, that we painstakingly crafted, just dissapated into the aether. There was no choice but to DF with an entirely new group. The second group I ended up with was absolute garbage. We had to spend another five to ten minutes explaining the fight, and we never got as coordinated as the first group.
If the first group had one more chance, with enough time to spare, I'm positive we would have won that fight. I'm sure there could be something that can be done to help the time management aspects of the fight, without having to nerf the dragon into a puk. The real difficulty isn't the fight, but rather coordinating a group of people, mostly entering the fight willingly blind, within the time limit.