Thank you for your comments
Firstly, I have avoided taking Captains in this list because they actually don't provide me with as much benefit as the Lieutenants do, as I receive a +1 to hit in most circumstances naturally, and (at time of writing) the Warlord Trait would provide +1 to hit to any unit that otherwise wouldn't get it. I also have access to Wisdom of the Ancients, for the same re-roll 1's bubble centred on a Dreadnought.
As for the Executioner, I took the plasma-variant as the las-version is inherently weaker against Knights and other units with invulnerable saves.
I have yet to run this list through the new-codex, so all of that logic may be completely skewed!