Allan,
This, being the Crew Research area (passengers, crew...they're all people), is unfamiliar territory to me, so I beg everyone's patience while I pay a brief visit.
I share your belief that Murdoch didn't commit suicide. I can't say for certain that he didn't, so I'll always allow for the possibility, however slight in my estimation. It's just that I don't agree with many of theories given regarding motives he might had had to end his own life; plus, I see no reason not to give credence to Lightoller's description of Murdoch's final moments.
At the same time, I make every effort to avoid engaging in hero worship. On the one hand, his own record and the rememberances of those who worked with him point to his being, as you said, "an excellent master mariner and officer." On the other, he was at the conn when the ship struck the ice. I keep both in mind when evaluating him.
That said, I take issue with the way you stated your last paragraph above. At first, you stated that Murdoch failed to keep the watch as he should have. By way of example for your assertion, you mention the lack of proper lookout. Later on, you state that Lightoller kept a continuous watch, with the insinuation that Murdoch did not do the same. My comment to this would be that you are talking two different subjects here, which makes it difficult for me to respond.
On the issue of lookouts, I think that extra lookouts should have been posted during Lightoller's watch and maintained through Murdoch's and Wilde's watch rotations. The failure to do so implicates the command environment aboard Titanic, rather than any individual deck officer's competence. Naturally, Lightoller or Murdoch could have called for more lookouts and the reason why they did not will evidently remain a mystery. If I put myself in their shoes, look at the situation with the recorded attitudes held prior to the disaster, I would then speculate that the clear weather Titanic was experiencing gave the crew no cause to call up the extra lookout. But why would they conserve such assets? Extra lookout duty impacts the crew duty rotation...maybe they wanted to keep fresh bodies available for the lookout later on. A tired lookout man is not an effective one, and there were many miles to go before Titanic was clear of the Grand Banks. I'm not saying this is the reason, it's just one possible scenario that comes to my mind when I ask the question. There could be any number of other reasons, just as valid.
Back to keeping a continuous watch. I don't see where Murdoch failed to keep a continuous watch. As far as we know from the facts, he was right where he was supposed to be...on the windward wing, looking ahead on Titanic's track. Given the available evidence, the argument can be (and has been) made that Murdoch was actually first to see the ice and had already ordered a turn before Fleet reported to the Bridge. Whether he did or not is the subject for debate, but I don't think anyone will contest the assertion that Murdoch was giving orders almost simultaneously with the warnings from the crow's nest. I see no evidence that he was figuratively asleep on the job.
I would assert that from Murdoch's perspective, the ship was going to clear the ice. In that situation, his greatest miscalculation would have been the extent the ice extended underwater. In this, illusion of the type that you have described elsewhere may have played a part. Would Lightoller have made a similar miscalculation? We'll never know. Lightoller said he would have seen the ice in time to avoid it. Maybe Murdoch thought the same. But would Lightoller have been more effective than Murdoch in avoiding the ice he couldn't see? Again, we'll never know, as far as I am aware.
Taken together, I see no evidence that points to Murdoch personally not keeping a continuous watch. I would like to know why extra lookouts were not posted, especially since Titanic was described by surviving crew as nearing the region of ice as early as Lightoller's watch. That subject, though, is grist for another mill.
Parks