I'm no expert but I've seen worse!
I had 2x8800GT in sli that hit 92 degrees at full load. Mind you my PSU did blow up soon after and took out one of the cards but I'm pretty sure that was unrelated ha ha
I'm running a HD5870 that hits 75-80 at full load (89 in furmark stability test) and it shows no ill effects thus far. I'd say you're good unless you start to see graphics errors or crashes. High temps can reduce the life of a card but unless there is obvious failure you are within the safe range.
It wouldn't hurt to take some measures for extra cooling though, you can never have too much cooling!
James