Certainly, it is the job of your solicitor to make sure that things are in order; but consider this:
1. If he had been given a proper official copy of the death certificate and had paid out what would (with 20:20 hindsight ) have been wasted money getting it translated\verified would you have been happy with the extra expenditure?
2. If he had said to you - "I have been given this copy of what the other side say is a death cert; I'd like to have it translated or verified, just in case there might be a problem with it" would you really have said yes, go ahead and spend the money?
Certainly, it would be nice to have been asked, but if your solicitor was told that there was a death cert. available, and was given a copy of a document purporting to be just that, then I don't think this is really his fault.