Took him down last night on Bristlebane. Had 6 groups avg 65. There are 6 guards around him. They are not instant respawn, but have a short respawn timer (the 6 mins listed below is very close). We accidentally pulled the guards first. What a mess that was. Got them killed and while rezzing the dead,...here they come again. The only way to completely clear agro was to die, zone out, or camp (/q).
Second pass was somewhat better. Enter from the SolB side. After you come out of the small bldg just before the Gatekeeper's, there is a room on the left. Have your forces stay in that room. You have to move quickly, so have several kiters ready. Pull the guards to the entrance and keep them there as long as possible. When the guards are gone quickly rush the Gatekeeper. For his level he is not that difficult. The hardest part is keeping the guards out of the fight. If the first kiter dies another has to be ready to keep the guards entertained. We had one guard stay behind and off-tanked it while the other jumped the Gatekeeper. He dropped fairly fast, but the kiter died and the guards returned with about 2% hp on the Gatekeeper. It wasn't pretty, but we won. Then we had a rogue drag all the bodies to the front for rezzes.
Sorry for the book. He dropped the Rogue 1.5 epic piece, the shoulder pads, and a crap Scorching Flame Earring. Loot sucks for his level.