I don't think that Death in Venice operates on the premise that a "life of sensation" is worthwhile, whatever the cost. Mann's story is a complication of the traditional morality tale, and Aschenbach's demise is not a result of his giving in to the pursuit of beauty and visceral experience, but of his previous, total rejection of this kind of surrender. Aschenbach, we are told, lives like a "closed fist," and for this reason is completely unequipped to deal with the combined experience of visiting an unfamiliar and sinister place, and of encountering a boy who provokes a strong physical and emotional response (on a sidenote, occasionally I hear someone label this as a homophobic text, but they are entirely missing the point, I think. As in Henry James's Daisy Miller, Death in Venice, on one level, illustrates the way that forces outside of sex can make sex, or the desire for sex, fatal. It has nothing to do with the act, or desire, itself). It is Aschenbach's perpetual need to take the proverbial "high road" that makes his foray into the world of the sensual so disastrous.
The story is brilliant. Not only does Mann address wonderful themes like the nature of art, artistic impulse, desire, repression, and Orientalism, even, but the writing and narrative trajectory are flawless.