Maybe on Obliteration warden the last Mob in Solemn ground or Quake Giant in odawa 1st But not 100% sure
Best are obliteration in solemn grounds, they drop m20 m23 rares and i read they can drop m18 elites, at m20 they dont give xp anymore and still drop loot, quake giants deals much more damage and got more hp and you will get xp on them at m20, they do drop m20's and m23's aswell. XiaoJie o7 Edit : quake giants may qbe best since they are more packed and you can gather them by more than 5, but you will have to loose xp if you want to sit at m20!