Hey m8. I feel your pain regarding the Sacnoth Vanquish. It was the only thing I left out of my Leg. Eotn title but then out of guilt and a need for Vanguard points, I went back to vanquish it about 3 and a half times.
So firstly, there is a great guide in the community forum
http://www.guildwarsguru.com/forum/s...php?t=10262474
which has illustrations and explanations of the path through Sacnoth that will yield the greatest amount of enemies (i.e. hitting 250 kills, and leaving the bosses for the end). You will only need to stray from this path slightly to vanquish every foe in the area, and you'll also need to kill all those silly worms in the SW corner

.
As for builds, I agree with Luminarus that triple necros are ftw. On the minion master run: jagged,horror,vampiric,putrid bile, death nova, prot spirit, aegis and extinguish. I ran an earth-shaker warrior, with the occasional SY! Pre-prot, careful agro, knock-lock ftw! Say what you want about PVE skills, but they are extremely useful here esp. breath of the great dwarf, pain inverter, and finish him! for those pesky grawl rits.
Lastly, make sure you pin your heroes/henchies well outside of the burning forest. Pull enemies in groups of 1 or 2 toward your heroes, but then unflag them as they draw near so that they all dont stand right next to each other. Kill every single thing in the forest before attempting the boss group with Borrus the fire ele. His group alone will probably wipe you so be sure you wont encounter anything else when fighting him.
Best luck, i got the run down to under an hour easily, and I ended with a max Vanguard title, plenty of loot, and some very useful green weapons for my heroes