So this discovery basically came about after talking with several people on the discord channel for a few hours, about whether or not Greenmage spells working with Hunter's Mark is actually intended. Hunter's Mark normally only works with weapon attacks in tabletop, but in Solasta, it also extends to all spells that make an attack roll (not spells that target saves or 100% accuracy spells like Magic Missiles). Whether or not that interaction is intended is not what this bug report is ultimately about, although it would be nice to have official clarification on that.
I knew Scorching Ray triggered Hunter's Mark per hit, but I did not think to analyze the exact interaction until I ran into a boss that could take enough hits to notice that something was VERY off.
Yes, you are seeing that correctly. That is TWELVE damage numbers.
It looks like what's happening here is that each hit of Scorching Ray is generating extra rolls of Hunter's Mark depending on how many total rays hit. If all 3 rays hit, each ray rolls the Hunter's Mark 1d6 three times instead of once per ray (essentially rolling Hunter's Mark a total of 9 times). If 2 rays hit, each of the two rays roll Hunter's Mark twice (rolling Hunter's Mark 4 times). I assume if only 1 ray hits, it rolls Hunter's mark once.
I have several other screenshots of my testing.
The above is with the first roll being a critical hit. The ray does 4d6 as intended with a critical hit, and the three 2d6s after that are the Hunter's Mark rolls that are tied to that critical hit. (The fourth 2d6 is the second ray itself.)
I was not fast enough to grab the actual dice with the demonstration above, but note that with a miss, there are only 6 damage rolls as opposed to 12. As stated earlier, what's happening here is that since one of the rays missed, the two rays that hit generated 2 rolls of Hunter's Mark per ray, instead of 3 rolls per ray if all three rays were to find their mark. I would assume that just 1 ray finding its target would generate 1 roll of Hunter's Mark.
Also, for the sake of removing all other possible variables, here's a Scorching Ray cast without Hunter's Mark.
But yeah, the point is, this is beyond 'definitely not intended' territory.
(And an unrelated bug report: I don't think a Lightning Bolt scroll is supposed to have a DC that low either. This finding came about as a test to see if spells targeting saving throws triggers Hunter's Mark, which they do not.)
EDIT: So my party hit level 5 and that means I can upcast Scorching Ray to level 3 for a fourth ray. Zero points for guessing what happened.
It looks like the bug is 100% confirmed to be about each ray rolling an amount of Hunter's Mark die based on how many total rays hit. In this case, 4 rays hit so each ray rolled Hunter's Mark 4 times (and my Greenmage one-shot the hardest boss in the EA).