There must be better ways to address the problem in an IPv6 environment with L4 termination or L7 application layer proxies coming to mind.
I guess not many ops-focused people have the luxury to care. Regardless of how you do it, you lose end-to-end connectivity and some visibility (the latter is BTW mandated by some standards like PCI).
For me however, for a load balanced service, the requirement is one name in the DNS and not a single IP (v4 or v6) address.
In a perfect world with perfectly architected and implemented TCP stacks and no security issues mandating browser DNS pinning, you're absolutely correct. In the imperfect world we have to live in, you usually stop fighting the windmills and use a single IP address if you have to get enough nines. Ivan