Probably worth doing, but I would have thought it has to be at least questionable how often it would be beneficial to recover the flight recorders in the absence of the physical evidence to be found in the wreckage - or vice versa. To understand the "why" you still still generally need to find the aircraft, even if the recorders have given you a good idea of "what" happened.
I'd also point out that for all the feverish criticism of the current method of recovering flight recorders from crashes into water, the odds are very much in favour of it working in this case, even if it does take a little longer than some people would like.