I don't think there is anyone who would argue the necessity of STOVL but I do feel that including it in JSF was not the best thing for us. The issues that it caused and capabilities that were lost are far to great. I'm not really sure what having a stealth CAS platform buys us. I think we would have been better off coming up with a Super Harrier the same way we did the F/A-18 and leaving out the F-35B.
Time may prove you right, but I'd argue there's no way to tell what capabilities you'll need in the future. The Brits in the late '70s/early '80s talked themselves into believing they'd never need organic carrier aviation or heavy amphibious lift, since in any conceivable conflict they'd be fighting as part of NATO. The French are finding all kinds of places where they're having to project some fairly serious power on their own, or mostly on their own (Mali, for example). Every conflict we've fought since Vietnam was in a place we never really pictured having to fight until we were fighting there. The more decks we have and more capable the strike assets we have, the better. It's a very dangerous assumption to make that the kind of strike warfare we've been doing for the last decade - total air dominance, limited anti-air opposition, premium on precision CAS - will be how we fight in the future.
Is the F-35B the perfect answer? Is there even any point in asking? The Marines threw their hat over the wall on that years ago. And the Harrier, at the end of the day, is still a 1960s design. I'm not for one second arguing that the procurement process was anything less than totally fucked up. But aviation history has plenty of examples of programs that were total back-alley abortions, yet eventually got the bugs ironed out and had successful careers.