Great posts by crystalstars and Indiscipline. It's nice to read some thoughts by people who actually understand vocal technique while appreciating James and seeing his technical issues at the same time. I'll just add my two cents.
James's technique was never perfect but which rock or metal vocalist's is? I think there are some additional reasons causing his decline to be more pronounced than that of many of his fellow singers. The chief one of them is the one that also made him such a great band mate - his nice and agreeable character. Watching all these early live videos, you get the feeling that he was like "just throw anything at me, super-high range, rasp, screams - sure, I can do it. And if I am not feeling well? Ok, I¨ll suck it up and power through."
He was probably never the type of guy to tell his mates: "Not feeling well, I am going to take it easy tonight." Or "my voice is shot, can we cancel the show"? It's just not how he is made up.
Later, watching the videos from Awake tour, you just have to marvel at his resilience - right after the injury when he should have been resting, he was still giving it his all. It was a make or break tour for the band and he was not the kind of guy to let them down. Even much later, watching Live Scenes, you still see how hard he was going - even though his voice was at 100 % that night, he still cranked out some really good performances.
And thanks to Jaime Vendera, James's vocal coach later down the road, we know that James would sometimes go as far as using cortisone injections for important gigs when he felt his voice could fail him otherwise (according to Vendera, cortisone will allow you to sing like your voice has been magically repaired, but it will also make you feel kind of invincible - you are at the risk of pushing way too hard, because you just do not feel the pain that would stop you from that).
Which brings me to the other point - vocal coaches. For all we know, James might have been working with a coach all these years till today and he could still have been easily ruining his voice. The only vocal approach that is tried and tested over long period of times is bel canto - and even many opera vocal coaches will still get it wrong every now and then, ruining their singer's voices by making lighter voices push too hard (Renata Tebaldi being a notable example), making large voices do the opposite or overusing some not-always-so-sound pieces of advice, like "sing to the mask".
When you get to the rock and metal vocal coaching business, the situation gets much worse. Many coaches are just phonies spouting nonsense , let's say about safe way of rasp.(Peple claiming that James did not use proper technique to do his Awake vocals are just ignorant - I mean, of you try to sing like this without proper technique, you won't finish a phrase, let alone a song. Let alone a whole show. But even with proper technique, this is not sustainable - or it is, but in the same way as smoking two packs a day is sustainable. Some people live long and healthy lives even then, but this is because they were blessed with resilient body, not because they had utilized a safe cigarette smoking technique.)
There are some other rock and metal vocal coaches who are not complete crooks, but still just make their careers out of giving some pretty basic advice, like drinking tea, doing good warm-ups etc. When it comes to complicated issues like navigating passagio, they are clueless. Most of them would probably say that singing with high larynx the way James does is ok, as long as "you do it properly". So, to finally make my point, even if James does use a coach, chances are the coach won't know what to do with his voice. In the end, with vocal coaches, as in many other lines of business, a more famous a coach, more likely he is to be not that competent, just good at making their clients feel good about themselves.
The other reason why James' decline is so marked is quite simple. He was gifted a once in a generation voice, not unlike, say, the greatest tenor of 20th century, Luciano Pavarotti. And if you go from a 16 cylinder voice (Bugatti) to just 8 (Bentley), people will notice it more than if you go from 8 to 6. James now might be just at quite ordinary 4 cylinders, but for many singers, this is where they started.
And finally, there are DT vocal melodies, with their often crazy high tessitura (something like the average pitch). It is not really the high notes James had to hit, like Fsharp in Learning to Live. It is just the sheer amount of time you have to spend hanging around high C or above to sing stuff like Images and Words. This is just not sustainable, unless your natural voice is even higher that a normal tenor, which James's is not. He just could sing it at the time so he did it, but any classically trained vocal coach would tell you that IaW songs would kill any tenor voice over time (compare that to ACOS, where James spends a lot more time in a normal tenor range, hoovering around E4, rarely going above G4 - how much more relaxed it sounds - it does because this was his sustainable range, this was where he really was Freddie 2nd ed.).
Add to that the amount of touring and you have a perfect recipe for disaster. Considering all of the above, you actually have to start marvel how, for so many years, James's voice held up so well, despite all the abuse. It seems that as late as in 2014 or 2015, he was still pretty impressive live, though he had always had off-nights.
As a fan, it grieves me as much as anyone to see him struggle like he does now. But he was always fighting an extremely uphill battle, the battle that almost anyone would have been bound to lose a lot earlier than James did.
And this is why I can't really stand some of the entitled and ignorant fans who keep bashing him and calling for him be fired. This is both mean and stupid. And hypocritical because, let's be honest, if overwhelming majority of people were in James's shoes, they would keep going too, like he does. (Indiscipline had a great post on what singers losing their voices go through in some other thread). Of course, wishing (and saying aloud) he would make the decision to retire on his own is something else entirely, there is nothing wrong with that, as long as you choose your words carefully, ideally the same words you would use when talking to your old friend. Because, and I might be a bit romantic or sentimental, the guys who gave me so many great moments are, in a way, like my friends. It is definitely not a typical producer-consumer relationship.
Sorry for the rant (This is by far my longest post at DTF). But where else should I speak my mind about the burning issues that no one in my normal gives a rat's ass about?