Not well. Ember can run to about sortie 2 level, sortie 3 if you're lucky. After that her damage falls off terribly to the point that she's not even clearing trash. She's a great star chart frame and she's magnificent for trash clear that falls between Equinox "4 and forget" and Saryn "Stuff dies too fast to spread infection". If you were to pair her with a single Saryn she'll never have anything to kill until the point that Saryn slows down and then she won't do enough damage for it to matter.
I don't mean to trash the frame as I love Ember and used to play her as short range, high damage even before the 'nerf'.