Ah well, finally. I don't for a minute believe Evans quit willingly.
As for who to keep and who not to keep: Get rid of Jordan, or give him something useful to do. We all know that he can be very funny and engaging - but on Top Gear he sadly makes the distinct impression of being his degenerated 90-year-old future self.
Harris and Reid are good, they improved visibly during the series, they just keep up growing into their roles. LeBlanc - he just plays a presenter. He needs to be more spontaneous, I don't know if he can pull that off. Perhaps when being placed opposite Reid, he'd be better.
Coming from someone with probably an equally terrible German accent: No, it's not that. Her problem - or rather, the overt symptome, I'm explaining my take on the actual reason for it further below - is that her "funny" remarks appear to be a desperate attempt at "I want to say something funny, too!" while being (mostly) totally unfunny. And this also seems to be her own work, not some bad script. At least that's the impression I get, because with a script, this bits should come out less hectic.
That she is, occasional difficulty to find the proper English expression notwithstanding. But she is clearly out of her depth doing a presenter job in English. She is fine talking about technical aspects of driving a car, when her racing driver experience gives her credibility and even the clich? "German seriousness" actually comes into play beautifully, but at least at her current level, having a casual, humurous conversation in English with a bunch of natural English-speakers in front of cameras and a studio audience seems to be too much of a strain on her (understandably), and that stress shows. As a result, she tries too hard.