Warren, considering that lot's of airlines regularly operate (or have operated) A343s into Joburg, I doubt that it's really that much of a problem...
Airlines that I know of that have or are operating A343s into Joburg on a regular basis are Lufthansa, Virgin Atlantic, Iberia, Austrian Airlines, Air France, Cathay Pacific, Olympic, Egyptair and, obvious through this incident, Emirates. Air Mauritius also flies it's A340s to Joburg from time to time (not sure how regular this is, but I used to see them at JNB
quite often), but I'd say that they probably don't really count because they're not flying off on a long haul from there.
So I guess that the hot/high issue itself probably isn't that bad.
P.S.: Although I must admit that taking off from JNB
one quite warm evening on OE-LAK (named "Africa") on Austrian's flight to Vienna (a few years back, when OS
still flew to JNB
), I was quite happy that the runway in JNB
isn't really all that short - although, taking off in a B732 on the way to Bulawayo in the same conditions, I was glad about that length as well...