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I think I'd definitely need to do something if I wanted a single surface throughout as there is an area about 2 ft long which drops over a period of about 3 inches a height of 2 inches. So a very steep drop over a short distance. After the 2ft it gradually settles. I'm vaguely considering getting a big drill and taking all the concrete out then levelling but realistically that's beyond my abilities. Would solve a lot of problems though.
Do you need to feather/taper? Will be much easier without but might not work with your door at the other end of the room.