I have an i7 4790s and a GTX 970 and get around 50-60 fps in Mor Dhona. On Gilgamesh.

I haven't checked during peak hours, though.

Normally my game runs around 150 fps so Mor Dhona DOES cause a slow down. For everyone.

What is your framerate outside the game's most densely populated area?

Also, do you have NVidia Geforce Experience? If not you can download it. It will set the game to optimal settings (which will probably be maxed out or close to it, this game is nothing for a 970)