I was re-reading this interesting thread and would like to make a couple of observations. I have no trouble accepting that avoiding pain can be a prime method, even a goal, of finding pleasure. This would be true either by an isolated act, or concurrently with a pleasurable one.
In his letter to Menoeceus Epicurus said: "“When we say, then, that pleasure is the end and aim, we do not mean the pleasures of the prodigal or the pleasures of sensuality, as we are understood to do by some through ignorance, prejudice, or wilful misrepresentation. By pleasure we mean the absence of pain in the body and of trouble in the soul.”
The point about anyone killing themselves to avoid pain if it was as simple as that to be Epicurean needs some attention for two reasons. First, I think killing oneself is not an option for Epicurus outside of hastening death when death is naturally imminent. Killing oneself outside of that circumstance as a means to seek pleasure, as Epicurus meant it is impossible. It is impossible because you can never experience pleasure if you are dead. Therefore to kill oneself is a violation of Epicurus' teaching of how to attain happiness. You cannot say killing yourself to avoid pain is ever consistent with Epicureanism (with the exception I stated above) either in attacking Epicurus or in ignorantly believing such an act is consistent with Epicureanism.
The point I think needs to be made is that you can't just say that your whole goal is to avoid pain. If so, then you can just kill yourself. Your goal is to live pleasurably, which requires that you live, being alive being a good/pleasurable thing unless you are in a situation where you are guaranteed more pain than pleasure). Treasuring life in such a way is a positive activity.
Secondly in the thread here, as far as the virtues go; I think Epicurus said pursuing one virtue, Prudence is enough.
"Of all this the beginning and the greatest good is prudence. Wherefore prudence is a more precious thing even than philosophy: for from prudence are sprung all the other virtues, and it teaches us that it is not possible to live pleasantly without living prudently and honorably and justly, (nor, again, to live a life of prudence, honor, and justice) without living pleasantly. For the virtues are by nature bound up with the pleasant life, and the pleasant life is inseparable from them.” Letter to Menoeceus.
As a subset of the virtue of Prudence, then, I have no real issue with saying "do no harm" since refraining from harmful behavior is prudent.