I'm pretty much in agreement with Sophia here. Class-oriented deities are rather too "unrealistic" for my tastes, and I'm inclined to opt for a more polytheistic approach, where possible. I would go so far as to include priests in that as well -- in the polytheistic societies I know something about, even the priest of, say, Apollo, would offer worship to (and therefore have piety with regard to) others in the pantheon. As both Sophia and Caelyndd point out, this offers a way to make the "evil" deities fit.
I, too, use separate PP totals per HM1.
The problem here, of course, is that the canonical descriptions push heavily toward side-by-side monotheisms that may tolerate some
other monotheisms, rather than true polytheism (to some extent reinforced by, e.g., the rules in HarnManor, or the rigid church structures). There's a need to flesh out the creaky framework. Religion in Harn publications has always been rather thin on the ground (where are the myriad temples, shrines, and holy sites?), and someone opting for a polytheistic approach (or for that matter even a developed quasi-monotheism) needs to place
many more such locations and opportunities for worship. If there really are hundreds of demigods and lesser divinities, where are their
places of worship?
That being said, I think you could work up a justification for a monotheistic drive on the part of worshippers of, say, Larani, if you wanted one.
You may also want to consider is syncretism; I wouldn't be surprised of Ivinians visiting Azeryan or Karejia were told that Sarajin is really
Finally, I allow invocations (per HM1) without much concern. After all, as Sophia points out, they don't have a guaranteed success (and, indeed, I wouldn't allow the player access to the mechanics). In addition, the effects described in the rules are merely guidelines for the GM, to be varied as circumstances dictate.
Another point that has come up several times is captured by Caelyndd's statement:
I wouldn't use invocations either if I used HM. I let priests use Ritual Magic in GURPS which is really subtle and never could create "proof" of divine intervention or magic.
There appears to be a feeling that spectacular miracles somehow create irrefutable proof of the existence of the deity involved and therefore shouldn't be allowed in a "low magic" environment. Most of us would describe "the real world" as just such a low-magic (or no-magic) environment, yet miraculous healings, for example, are attested for many religions (even today) without their constituting irresistible proof to others. See much medieval hagiography, but also, for a non-Christian example that comes to mind immediately, the life of Apollonius of Tyana. Healing springs, oracles, visions, laying on of hands, etc. can all be abundant without offering "proof."
For some good discussions of the social role of miracles and holy people (which can provide some excellent suggestions for game play, too), I'd recommend starting with Peter Brown, Society and the Holy in Late Antiquity
and The Cult of the Saints: Its Rise and Function in Latin Christianity
, and Raymond Van Dam, Leadership and Community in Late Antique Gaul
and Saints and Their Miracles in Late Antique Gaul