Meldrath seems to always be up (spawned). He is in the minotaur caves with 2 guards. They will aggro you along with Meldrath even if you get them down to gray. I am doing the Ivy etched quests without Defiant armor or a mercenary so it is a bit rough. Though I do use the timed-AA skills and servant that give you short duration buffs, which made Meldrath doable at level 40.
I snared him and ran back towards the windmills. Taking out one of his minotaur guards, with a gnome guard taking out the other. Then I DOTd Meldrath as he came along towards the windmills. Luckily the necro "fear" spell (I forget the name) causes the mobs to drop aggro while you just sit there doing nothing. It was still a tough fight with the AA buffs but Meldrath doesn't have too much HP so I was able to nuke him down at the end.