I just did this fight solo after reading your forum posting because I was having trouble with this fight as well. Level 50 Gunnery Commando
I used a stim that raised my endurance by around 80, kited alot! during phase 2, used a healing med pack, and made sure to keep him stunned or slowed as much as possible. I moved around alot in this fight and did not change Dorne's commands around at all. she DPS'd / healed.
You will end up blowing every single cooldown you have during phase 2, so do not use them in phase 1, like people have already stated on the forum. During phase 2, you will notice he puts a debuff on you immediately that increases the amount of damage down to you and stacks. If you have 2 stacks and he hits you, say good-night. You want to hide behind pillars continually and make sure you do not get sucked in during the AOE storm he does.
Best of luck to everyone, by far the most epic fight I have done in the game solo. I wish I had recorded it... so freaking awesome.
BTW, I killed him with about 1,000 HP left! on my commando. :-D