Yes 70c is too hot, with a Volcano 7, you should be getting better temps than that.
Check the seating on the DIE, make sure its making good contact.
If you,re using thermal compound, and you should be, instead of the thermal pad, use Artic Silver III, and barely coat the DIE with an even layer, thinner than a sheet of notebook paper, do not gob it on, in this situation less is better, properly using Artic Silver III could lower your temps as much as 8c.
I know some people have run their machines at higher temps as stated, however I prefer my temps below 50c.
FYI 90c is the kill point for the AMD XP according to the AMD website.
Details, Details, Its all in the Details, If you need help, Don't leave out the Details.