Felony Murder, "Malignant Heart" (Grossly Reckless) Murder, and Victim's Killing of Accomplice

The post about how surviving home invaders may be charged with murder after the victim shot and killed one of them in self-defense led to comments criticizing the "felony murder" rule. To quote the Georgia statute, there are three ways to be found guilty of murder:

(a) A person commits the offense of murder when he unlawfully and with malice aforethought, either express or implied, causes the death of another human being.

(b) Express malice is that deliberate intention unlawfully to take the life of another human being which is manifested by external circumstances capable of proof. Malice shall be implied where no considerable provocation appears and where all the circumstances of the killing show an abandoned and malignant heart.

(c) A person also commits the offense of murder when, in the commission of a felony, he causes the death of another human being irrespective of malice.

And people have long been troubled by the "irrespective of malice" nature of felony murder; even felons, the theory goes, should be punished just for the crimes that they intended, not for a murder that happens unintentionally and even unexpectedly during that crime.

But I wonder what people think about allowing criminal liability under the "abandoned and malignant heart" theory here. That theory, often called the "depraved heart" theory, essentially extends murder not just to intentional killing deaths, but to grossly reckless killings. To quote one recent case (this one from Maryland, but these principles are generally treated the same throughout the country),

We have described depraved heart murder as "one of the unintentional murders that is punishable as murder because another element of blameworthiness fills the place of intent to kill." Depraved heart murder constitutes "the form of murder that establishes that the willful doing of a dangerous and reckless act with wanton indifference to the consequences and perils involved, is just as blameworthy, and just as worthy of punishment, when the harmful result ensues, as is the express intent to kill itself." "The critical feature of depraved heart murder is that the act in question be committed under circumstances manifesting extreme indifference to the value of human life." We elaborated:

A depraved heart murder is often described as a wanton and wilful killing. The term 'depraved heart' means something more than conduct amounting to a high or unreasonable risk to human life. The perpetrator must or reasonably should realize the risk his behavior has created to the extent that his conduct may be termed wilful. Moreover, the conduct must contain an element of viciousness or contemptuous disregard for the value of human life which conduct characterizes that behavior as wanton.

… [D]epraved heart murder involves "the deliberate perpetration of a knowingly dangerous act with reckless and wanton unconcern and indifference as to whether anyone is harmed or not."

Again, here's the fact pattern: Robber Rob and his accomplice Alec are engaged in armed robbery of victim Vic, and Vic pulls out a gun and shoots and kills Alec. Rob didn't just commit a felony here; he did something that was extremely dangerous, both to the victim and to the accomplice. It is hardly surprising that, in America, a robbery victim would have a deadly weapon available to defend himself (especially, though not only, in the victim's own home), and would be willing to use it. This sounds like "extreme indifference to the value of human life," and "wanton unconcern and indifference as to whether anyone is harmed or not." Even if you don't approve of felony murder liability, would you approve of depraved heart murder liability?

Here are a few possible answers:

1. The felony murder rule is just fine generally (especially when it's limited, as it is in many states, to violent or otherwise highly dangerous felonies, and when it requires at least some foreseeable risk of death, perhaps under the rubric of "proximate cause"). Rob engaged in felony robbery, so he should be punishable for murder as to any deaths that his conduct caused, even indirectly, including Alec's.
2. The felony murder rule is bad, because it risks liability without a showing of "reckless and wanton unconcern"—but the depraved heart murder rule is good, so Rob should be punishable for murder as to Alec's death.
3. The felony murder rule is bad and the depraved heart murder rule is good, but Rob shouldn't be punishable for murder, because embarking on an armed robbery doesn't rise to the level of "the deliberate perpetration of a knowingly dangerous act with reckless and wanton unconcern and indifference as to whether anyone is harmed or not."
4. The felony murder rule is bad and so is the depraved heart murder rule. Only truly intentional killings should count as murder (and depraved heart killings should generally be manslaughter or some such).
5. Under either rule, Rob shouldn't be punishable for murder, because he should only be liable for unlawful deaths directly caused by himself or one of his agents (such as by accomplice Alec), and Vic's shooting of Alec is lawful.
6. Under either rule, Rob shouldn't be punishable for murder, because he shouldn't be liable for the death of an accomplice. If Vic had shot at Rob and Alec but inadvertently killed bystander Betty, Rob should have been punishable (either under the felony murder rule or the depraved heart rule). The killing of Betty would have been accidental on Vic's part, and thus likely not unlawful on Vic's part; but it would have still been indirectly caused by Rob's conduct, and that's enough to make him a murderer as to Betty. But the same theory shouldn't make Rob punishable for murder as to Alec, if Alec had been the one whom Vic shot.

I'd love to hear which answer people endorse here (and of course other options are also potentially available).