Without completely rehashing the conversations that came to light on Discord, I'll summarize some of the key points.
Essentially, the DC10 is one of those elements that the current sequel design retains from TNP; an argument could be made that it's vestigial, or that it's one of those "ship of Theseus" situations -- but on the other hand, you have to start somewhere. Where it seems to be at loggerheads is in the particularly sequel-ish notion of adding flat modifiers into the mix. To wit (and, in short) if the assumption is that your combat rolls will always add your highest stat (i.e. a +2) then the DC isn't really 10, it's more like it's actually an 8.
So, one direction in which that conversation forks off is, how do we incentivize variety in combat modifiers? Well, essentially you would have to structure a class' basic features such that the +2 was always (or at least, often) adding dice to the pool. The math tells us that a +1 increase in attack is about equal to adding one more d6 to the pool, so the bigger incentive is going to be adding the die, because it also adds a d6 of damage (and not just +1 damage.) Alright, but since our acceptable range of modifiers is already so limited (+0/+1/+2) how do you iterate that idea over, say, 6 different classes? This idea also solidifies the notion that the attribute array would have to be limited to a single +2 -- otherwise, you'd put a +2 into your attack stat, and a +2 into your "dice pool" stat, because that's a no-brainer.
Now, this sounds like a nitpick, but part of the reason I chose DC10 in the first place is because of the ergonomics of it; 10 is the first double-digit number, it's also ingrained in 10-fingered humans (which is likely the reason the base-10 number system exists.) But as I've said before on the blog, where it really came from was if you strip away your +3 attribute and +2 proficiency when trying to hit an AC15, the math of +0 vs. AC10 is exactly the same. But that's talking about d20 math, and the sequel isn't in that paradigm at all, anymore.
So the first idea that occurred to me was to strip out the modifiers; to keep the math the same, we'd have to arrive at a DC8 -- at least for a basic combat roll involving 3d6. Well, 5 is a nice starting point (for the reasons mentioned previously) and adding the number of dice to that gives you 8. So maybe the DC is "5 + [number of dice]" instead of just a flat 8. What I quickly found with that is the DC escalates slightly, for almost no meaningful change in hit-chance; this felt like it was adding overhead to the mechanics with no subsequent added functionality.
Building off of that, the next idea that popped into my head was, "what if the DC was [number of dice] * 2?"
What this would functionally do is lower the DC of the 'basic attack' down to 6, giving a much higher hit chance and reliable damage output; it also creates a cap where having 6 dice in the pool bestows steep diminishing returns, and 7 pushes the DC into impossible territory (i.e. 2d6 cannot equal more than 12, and 7 dice would create a DC of 14.)
With a little help from the people who brought you Strike! RPG, I was able to get a very precise calculation as to what the math would look like on this (rather that just ball-parking it, with my limited mathematical knowledge.) Using the two lowest possible dice (which still produce a hit) for the attack roll, and the remaining dice for damage, we get:
3d6 DPR = 3.58
4d6 DPR = 5.40
5d6 DPR = 5.93
6d6 DPR = 3.21
The question then is, does this give us enough flexibility to build out the mechanics? Clearly, the answer is "not quite" since this would effectively cap the number of additional dice you could add to the pool at 2 or 3; the only way you could get around that is to cap the DC at something like 10 -- go figure.
The other thing we have to remind ourselves is that without using modifiers, "only 5s and 6s matter" starts to creep back in. (It genuinely makes me wonder if the Arkham Horror-type games are built around the assumption of 5s and 6s being successes, for this same kind of reason -- or it could just be a coincidence.)
And that's pretty much where I sit, at the moment -- stuck between a rock and a hard place. It seems silly to have flat modifiers that don't matter, but it seems nearly impossible to diversify those numbers, either. On the other hand, if you go back to the paradigm of "attributes only matter for skills" then we've just reinvented d20 TNP (seemingly right down to the DC10, even) -- almost like building that ship of Theseus I mentioned at the start.
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April should be a lot better for sticking to the planned schedule of 5th/15th/25th, so check back on those dates, for more!