Perfectly doable without it. Playing on hardcore myself. If you want easy mode then grab pre-gen black orc fel chosen and stick to green brutal dudes.
Is not that Lord's Gate unlocked via exploring mountains? Or it there another one I am not aware of?
Oh it is not something to do with the Thorngate?Scout mountains until you get a wow you discovered the entrance to the lords gate! result and then do the lords gate assignment and youre on