Maraudon is the sweetspot imho from 43 to 46, given that you push through the quests to finish the scepter. Just use the scepter and backtrack the turtles + elementals + oozes + dryads, then reset. Just be careful not to die and not to reset too quickly, as getting out and back in with the scepter is a significant time loss. After 46, ZF gets substantially easier due to the new Arcane Explosion rank.

Same story with Sunken Temple 51-54 after a level of Hinterlands questing and before hitting BRD which is also unnecessarily hard at 51. The troll circle (uppermost layer) in ST yields around 12k xp alone and should be doable in 8-10 minutes with ridiculously low effort.

You should be able to sustain 50k xp/h in Maraudon (after the quest/scepter run) and 50-60k in ST and BRD. 70k in LBRS if you only do orcs/trolls. All in simple 1-2 group pulls with a lot of drinking, straight forward tank and spank and no crazy skip/mass-AOE shenannigans.