What a mixed bag this thread... Please, carry on with the myth of an omnipotent Rossi calling the tires he "wants" if that gives you some onanistic pleasure: but VR certainly wasn't the only rider calling for a harder front, -- Marquez anybody -- and there was (or wasn't it there) a majority of riders voting for that tire, after all. And let us conveniently forget that Vinales (or better, Yamaha factory's) problems began when the "soft" front tire was still in use, well before the harder one became standard; and let us also ignore that both Vinales and Rossi could choose the chassis they preferred, nothing was imposed by Yamaha.
Track results show that the 2017 Yamaha does have some real problems, which didn't show in the initial races but did suddenly and dramatically emerge at Jerez for both factory riders. The 2017 chassis even in its most recent iteration seems to have trouble working well at certain tracks. And typically when these problems emerge, they affect Vinales and Rossi, as happened also on Sunday when they were both beaten by Zarco on the 2016 bike. Because of that (and because Honda solved their problems and Marquez can now ride at his best again, with Pedrosa in trail) an initially dominant Vinales experienced a setback.
At Ducati, Lorenzo is now quite fast with new tires. But he has not been able yet to exploit the efficient wear curve of the rear tire that is one of the best characteristic of the current Ducati. He tries his old disappearing act in the first laps, and so compromises the rear tire early and spoils its performance for the second half of the race. So he leads for a few laps, then falls back as soon as the rear tire goes down one notch and handling the bike becomes even more physical. That's what happened to him on Sunday. Maybe he doesn't want to copy Dovi's tactics, maybe it's just his instinct.
The real story of 2017 is the complicated choice and unpredictability of the Michelin tires. That is what is badly conditioning everybody. But even in the current uncertainty, Marquez is efficiently chasing his 6th title. Chances are that he, rather than Rossi, will reach that famous number 10.