I don't think there is a problem other than he is now her superior yet she appears to be 'leading' the investigation. I've watched 2 qand a half episodes and it's looking as if they've sorted things out between them. And, as it really has no bearing on the story, that wasn't a spoiler :-)
As for the "Guardian trashing it", it is just one person's opinion. I never read what the critics have to say about any of the programmes i watch, preferring to make up my own mind. Stephenson in the Sunday Express is critical of most things other than reality tv?