I think that it might be overstating things to say that the "artistic temperament" "is a disease which arises from men not having sufficient power of expression to utter and get rid of the element of art in their being."
Though it is very true that the emotional extremes characteristic of that temperament usually arise out of the tension between intense desire to create and various impedences to creativity, the simple fact is that having difficulties being creative isn't part of the artistic temperament. The vast majority of humans have difficulty being highly creative (which is sort of a tautology, if most people could be highly creative, then that level of creativity wouldn't be "high", would it?).
The difference is that those with a certain temperament experience a felt need to be more creative. So even with modest native talents, these individuals will struggle to produce art, sometimes at immense personal cost.
And that's a good thing. After all, a certain number of highly talented people are also very lazy. Even the most talented person, if lacking in the simple drive to create, will create as little as the person that has no talent at all, and probably less if that other person is hungry to create.
Shakespeare might not have had enough drive to try and use his writing to remake England (some of his contemporaries, and at least one of his cousins, did try, and died for it). But he certainly had enough drive to make his way in the uncertain and highly competitive (sometimes literally cut-throat) world of Elizabethian theater rather than in some less creative field. And he often cared passionately about the themes he addressed in his writing. The historical context in which he wrote Othello is particularly enlightening and a reminder that the most truly liberal values are not an invention of the modern era (nor do we need to go on inventing silly new ways to be "progressive", but that's speaking as a classic liberal).
The man cared about his art, he wasn't just doing it because it was the easiest way to put bread on his table. He had personal reasons to strive to be the best, he also had causes to which he lent his art. He wasn't tormented, as the artist who is denied the ability to create, but he wasn't content.
And he most certainly wasn't ordinary.
Still, I agree that there is too much of a tendancy to believe that an artist must have great difficulty creating for the art to be worthwhile. In the end, the text is the text, whether written in blood or indigo. Styling oneself as a superior artist because of an inability to create is the most petty sort of vanity, a childish deliberate despite against anyone having more.