It’s like you were able to pull Feats and Challenge Ratings out of D&D 3.0 and retrofit them into your 1st Edition game, almost seamlessly. Or pick up a 1st edition copy of Tomb of Horrors and run it, practically verbatim, with D&D 3.5 rules.

Having said that, it’s still time for me to open a new thread on the Trollbridge.

As far as I can tell, the official 7.5 way to do it would have the goblins dividing 29 that second round (TTYF blows one up and counts fully towards the HPT).

My friend Russell suggested you could track the magic/missile and weapon damage separately…counting it in the totals to see who wins the round, but then only comparing the weapon damage to see how much (if any) damage the losing side takes. I’m unsure whether the added complication is worth it. That would mean in your example that the only damage the goblins would be taking would be from the spell…

Wally the Wizard (Lvl 7, IQ 50), and his rented stooge, Wilbur the Warrior (3D+10), are attacked by five rather optimistic MR 25 goblins. Wally lets loose a 2nd level TTYF (which costs him one point of kremm, all he thinks this is worth). The goblins roll up 124, Wilbur rolls a 19, plus 100 from the TTYF. The goblins win, and Wilbur and Wally split 5 points of damage plus 3 spite; one of the goblins dissolves into pink mist. Second round, same tactics: The goblins roll 92, Wilbur rolls 21, plus 100 from TTYF. Another goblin dissolves into pink mist, and the survivors split four points of damage. (There is also some spite damage, but it seems irrelevant at this point.) Third round, same tactics: The gobins roll 76, Wilbur rolls 20, the TTYF is good for 100. A third goblin goes to pink mist, and the two survivors split the 20 points of damage Wilbur did between them. Round Four, the goblins either run away or die.

If we discount the “shock and awe” value of the TTYF, which I will admit that 7e seems to do, the goblins slaughter Wally and Wilbur after a turn or two. This would be a huge and, I think, unfortunate change. It may be what was intended; I will have to ask around among those who were there at the time.

p97: “Magic that does damage always counts as part of his side’s HPT.”
and
“Calculate Your HPT: count all damage that actually happens–points of magic taken, missile damage, and hand weapons.”

What might have been dropped accidentally is a step where after the winner of the round is determined, and the difference between the winning and losing totals is calculated, the difference is further reduced by the magic and missile totals of the winning side, so as not to double-count. On the other hand, since the magic and missile totals of the loser have already reduced the damage the losing side would take, wouldn’t that be double-counting as well? So it really should be only the excess of the magic and missile totals of the winner (if any) that gets subtracted from the damage.

In the end I think it’s much simpler to just do what the rules actually say: count everything that does damage, compare and subtract. Then if the result seems strange (like one side’s total is from nothing but missile and magic, and the other side only melee, so you really would be double-counting every point), the GM can adjust it for that round, just like he can adjust anything.