I really don't get how you can say this isn't an issue?
I can say that because everything that I have seen here completely antidotal, and essentially subjective laypersons interpretation.
If there is an issue, those that are qualified to make that assessment will do so.
Loss of capacity bars isn't anecdotal, it's fact. And as pointed out upthread, if you find that the $40k car you expected to be able to do your commute in for at least 5 years (based on Nissan's 80% after five years) is unable to do so owing to capacity loss after a year or two owing to your local climate, you are going to be mighty pissed. If Nissan doesn't take action soon to both compensate the owners who have already suffered losses, and to change the way they sell/advertise cars in hot climates, they are going to suffer the same kind of reputation hit that other companies who ignored complaints from customers have, even ignoring any lawsuits that result. Especially since the average Leaf owner is supportive of the technology, and isn't looking for an excuse to criticise it. And 'those that are qualified to decide if there's an issue' are going to be Nissan's current and future customers, regardless of what company tech reps/lawyers/PR hacks have to say. If people aren't willing to buy your cars, there's an issue.
Eventually, what it will take will be capacity warranties. I think GM took the right approach with the Volt, using an ATMS and using a smaller proportion of the battery's total capacity even though that boosted the initial cost. I'd much rather see a company guarantee a lesser capacity for x number of years than quote a maximum that won't be achievable for the period of time most people keep a car.
Finally, re your methodology of quoting 5 or 17/~25,000 of Leaf sold worldwide (rather than just those Leafs operating in high temp areas like Phoenix) as being the appropriate denominator for determining if there is a problem. By that methodology, the Challenger's SRB gaskets only catastrophically failed 1 time in 50-odd launches, a ~2% failure rate, instead of the 100% failure rate in below-freezing launches. Which do you think is the appropriate method for deciding there's a major problem that needs to be addressed?
Obviously, NASA could have decided to scrub any shuttle launch where the temp was low enough to cause a potential failure, or they could have done what they in fact did do, re-design the gaskets. Nissan faces a similar choice; they can either refuse to sell the cars in areas with prolonged high temps (or only with warnings that much quicker degradation is to be expected, perhaps as much as 15-20% in the first year), or else they can re-design the battery pack. Just saying "all is for the best in the best of all possible worlds" isn't going to cut it.
[Edited to correct Candide quote]