The answer likely depends on 1) to what extent the firms rely on patenting, and 2) whether the firm can get around difficult examiners/art units.
Please provide anecdotal examples or experiences, if possible.
This is entirely anecdotal. I worked for years in a large medical products firm. Patents were essential and R&D spending was not impacted by patent office challenges. However, it is certainly possible that in other industries with faster product life cycles, pursuing patents is seen as less important. Even so, I kind of doubt it impacts R&D spending much. It is also possible that with small firms patent delays are a bigger issue.
Certainly in the case of my own patents we had several difficult examiners. In one case, in particular, my lawyer had to appeal to the examiner's supervisor when the examiner was completely misunderstanding the prior art. Generally speaking, we were successful in obtaining effective patents. A lot has to do with the quality of the patent attorney or agent.
It has been several years since I worked at a huge technology company but my two cents is that problems with and examiner here and there would not affect corporate strategy but a strong trend toward classes of inventions having reduced chances of getting a granted patent would.
The limited ability to get patents on business methods, software, anything that be reduced to a gist that seems abstract (almost everything), and DNA related patents should be causing companies to re-think ways to protect their R&D investments.