I tried to express this point back in the Force & Flow essays, but I’m not sure I succeded, so I’m glad for the chance to revisit it! I think I can answer your first question with the second. The range of a “miracle” is essentially the same as the range of “magic”, a concept that canonically applies to Heirs, Witches, Maids and Sylphs. 

Jesus’ story is imported into Homestuck in the story of the Signless–a Seer.
When Jesus comes up, John describes him as magic–just as he later describes himself, Jade, and Rose in the midst of her Witch roleplay.  (And yes, this does mean the Jegus meme had a payoff in the form of classpect exposition.)

Later on, Rose seems to more or less figure out how to roleplay a wizard. But when Dave thinks to ask, she makes it clear what she’s doing isn’t exactly casting spells in the typical sense.

Which makes sense, because Prophets aren’t typically thought of as being magic per se. If you think about it, the miracles Jesus performs aren’t really that different from what we might imagine wizards could do.

What makes them different is a matter of emphasis. Wizards are regularly linked to knowledge, just like prophets are. Hence the concept of the “wizard’s spellbook”. But for magicians, knowledge is typically a means to an end, it’s an answer to “how” the magic is performed.

Prophets also do magic, but for them the emphasis is on the knowledge itself as opposed to the spellbook. A Prophet like Jesus or Moses would typically claim their magic wouldn’t happen at all, but for their faith in and knowledge of their divine Source–God.

Just trade in the figure of “God” for the Seer/Mage’s Aspect (the Aspects are inherently divine-coded anyway, given that they’re basically Aeons), and there you go. Any kind of magic you can think of a Prophet doing through their Aspect is something I believe reasonably falls under their purview.

I’d simply put just as much of an emphasis on what the Prophet might end up saying as a result of their Aspect’s influence, which is probably even more interesting. Do their prophecies concern/affect/benefit primarily themselves or others? How does their Aspect influence what message they have to give, and how they deliver it?

A particular nuance to the pair might be a penchant for resurrections/raising others from the dead, particularly in ways that might otherwise seem impossible. Sollux pulls this off for himself by half-ghosting, while Terezi pulls it off for Vriska by guiding John’s choices.

Does this answer your question, anon? It’s a pretty dang good one, btw.