Seona was able to tag along (and trust me, at only level 62, that's all I was able to do) and the group (more or less full raid of 40) managed to get three of the four bosses down. Lady Sylvanas fell first in Undercity, then Lor'themar was taken out, and finally Cairne was downed. By this time, however, the Horde was able to regroup and it made killing Thrall impossible. To be fair, we did leave the hardest boss for last, and it showed. Naturally they carried me all the way, but I did what I could to help, stomping totems for example and helping summon people. Of the three achievements, I got two of them while dead. Still, it was a great fight and a ton of fun. Even better, I upped my Honorable Kill count, earning the achievement for 100 HKs.
What I love about the Kingship is their honor and compassion. We were unwilling to leave anyone behind after the wipe. I felt real kinship and strength with them. What's even more exciting is the fact that I know we'll go after Thrall again in the near future. There's always an excuse to get retribution on the Horde, and killing Thrall is a great way to do so. Hopefully next time they go for him, I won't be a level 62 just along for the ride. I mean, I hope to at least be level 70. ;)