Yes, can confirm this too, Sapphire 7950 Dual-X aren't suitable for mining.  
Had 8 cards of this type of which 7 died within weeks, one after another. Bought them new from pixmania.co.uk, about £150 per card, ... was thinking that it's a bargain but it was a total waste of money and time.

The last one still works (after about 2 months of usage) but isn't stable anymore and I'm afraid that it may die soon as well. Serial numbers of the cards were  A13500003XXXX.


The way they fail is:  PC shut down randomly  then at one point it doesn't start anymore, the screens goes black after windows start up logo. Some cards fail with sparks, one actually burned out filling the room with smoke, that was really scary, thanks God I was nearby to switch it off.


BTW: don't overclock them at all (use default settings only) and don't use more than 1 card of that type per miner, that appears to save them for a longer period of time, but it's still not guaranteed.


I'm trying to avoid all Sapphire GPUs were possible after this experience.