Well, I managed to do as an Unholy Death Knight after a few wipes. It was a bit tougher than expected. I was just trying to get an item off of him. It seems that neither Mione nor Raegwyn have revisited the encounter, so I figured I'd just make a post about it. It's also important to mention that I used blood presence during the fight. There are two umbrella reasons why the fight was difficult:
1) If Phase Punch stacks to 5, you're ported and Algalon ascends thus ending the encounter.
2) His damage output is relatively high. He's quite a fast-attacking jabroni. He was meleeing me for something like 9.7k with his MH and 4.4k with his OH while in blood presence. There is also perpetual magic damage during the fight from stars exploding to the quantum strikes and phase punches themselves.
With the advent of MoP, it is now possible to truck through the encounter before 5 Phase punches go out. It is a pretty strict burst dps check. The dps requirement of the fight is somewhere over 115k at least. When combat ended, I had about 131k dps. This is less feasible as a Blood DK. As aforementioned, I used blood presence during the fight because I was dying before I ever reached 5 stacks in Unholy Presence.
The best I could do is provide two screenshots: one screenshot of the chest in the background in addition to my dps, as well as a screenshot of the damage breakdown. I also elected to remove a lot of the clutter in my UI by gutting it (i.e. turning off some addons). I'll probably install a video-recording software when the lockout resets to "fraps" the fight just for completion's sake.
For whatever reason that you want to kill Algalon, it only really comes down to a strict dps check. If you're struggling with it, it might be understandable :x