My main issue with FGW has always been a lack of information when things go wrong. But that applies to ATW and XC in my experience, so I can't really blame FGW specifically. It is a problem with the railway industry in general.
That probably is because of what we staff on the forum keep saying - it's often a fluid situation, nobody can really give a time or a pathway as to what is happening, and the people sorting it out are busy actually sorting it out, not getting sidetracked into giving a running commentary which may turn out to be inaccurate anyway.
For example, today, I was stopped at a signal about Tilehurst. The pager said there was a problem at Reading West Junction, and 15 minutes delay. I went onto the PA, explained there was signalling problems and a delay, as soon as I finished, the train moved, straight onto the platform no stops, total delay less than three minutes. I'd have been better off saying nothing. But Control had obviously been told by Network Rail it was going pear-shaped, and they told us.
When there is serious disruption, for example on the train mentioned by the OP, or any of the dozens of trains mentioned in previous threads, nobody really knows how long it's going to take to sort it - but what is known is that the safest place to keep passengers is on the train, not start half-assed plans about ramps and walking along the track.
I had a train a few months ago, Box Tunnel was closed so it had to run Bath-Reading non-stop via the B&H. I announced this, gave my estimated running time (which was spot on!), and then walked through checking everybody's ticket as a means of interacting individually with every passenger. I found a few with ipods on who had no idea despite my numerous announcements before and while on the platform at Bath, but the doozie was when I reached the final carriage. One gent started screaming (no exaggeration) at me as why I had not been giving updates every five minutes (despite nothing to update), and told me in no uncertain terms that my going through (talking with all 300 passengers on the train to address any individual concerns and questions they might have) was not good enough, and the sort of rubbish customer service he had come to expect from FGW.
How can you please people like that?