In this post I'm not going to comment directly on Michael Heiser's interpretation of the divine council. Instead, I will sketch my general approach to the "divine council" in Scripture.
i) I have no antecedent objection to the notion that Scripture sometimes uses mythopoetic language–especially in genres suited to poetic imagery and/or polemical zingers (e.g. Isaiah, Ezekiel, Job, Psalms, Revelation).
ii) That said, as I've remarked on other occasions, one problem I have with many Bible scholars is their myopically textual focus. They act as though every text must be understood in light of another text. That the ideas or images in one text must derive from another text.
Suppose, for discussion purposes, that the divine council in Scripture is adapted from a pagan pantheon. Even if we grant that contention for the sake of argument, it only pushes the sourcing back a step–for what's the ultimate source of that framework?
When Jews or pagans attempt to conceptualize or visualize the divine abode and its residents, what supplies the raw materials for that imagery? Is it always a matter of chasing down textual allusions and literary parallels? Offhand, I can think of several potential sources:
a) The human family
The pagan gods are modeled on human families. Fathers, mothers, sons, daughters, sisters, brothers, &c.
Scripture uses fatherhood and sonship as archetypal theological metaphors.
Kings, queens, princes, princesses, mistresses, courtesans, courtiers, palaces, palace guards. Pagan mythology and the pagan pantheon make extensive use of these archetypical roles and images.
(a) & (b) also furnish the basis for palace intrigue and civil war, as younger "gods" strive to seize the throne.
Scripture is, of course, far more selective. God is a king, his Son is the heir. Angels are analogous to palace guards, royal emissaries, and courtiers.
c) Institutional religion
Priests, temples, temple guards, religious art and iconography, including hybrid creatures.
Not surprisingly, Scripture makes greater use of these conceptual resources.
d) The military
Ancient nation-states require soldiers and fortified cities.
In Scripture, this is used to depict the warrior-God with his angelic army–or should we say, air force?
In Revelation, the New Jerusalem is like a fortified city. The saints are inside while the damned are outside.
e) The natural world
Celestial temples or palaces. Sacred mountains with a divine palace on the summit. Storm-gods. Storm theophanies. Orbital bombardment.
Both Jews and their pagan neighbors lived in a social and physical world which often supplies the metaphorical palette to depict an unseen realm. That's not something they had to get from a text. That was all around them.
Why should we first reach for an Ugaritic parallel to illuminate an OT passage rather than considering the common source for many of these images and metaphors? Much of the stock imagery comes, not from a text, but from their physical and social environment. They got that directly.
iii) In the case of Scripture, this can operate at two different levels:
a) There's direct revelation, here the immediate source is from God. Even in that case, God made depict things in culturally recognizable garb.
b) Written revelation can become a storehouse of stock imagery for later Bible writers.
There is, moreover, a dialectical relationship between (a) & (b). On the one hand, written revelation is a source of stock imagery. On the other hand, God made reveal truths in stock imagery. So there's cross-pollination.