Sure. You are pretty spot on. If you do 60% with "disadvantage" (not the mechanic, but the concept), your hit drops to 0.60 x 0.6 or 0.36, roughly the 35% I would (personally) prefer. If you go to 65% as the base, you get roughly 42%, which is a tad bit high for me but perfectly acceptable.Just plucking these out for the moment. I'm going to take some (hopefully small) liberties with the math for ease of use. I believe you mentioned somewhere that a 35% hit rate would be more your speed rather than the 5e "60-65%" success rate you indicate. With that assumption in mind, let's make it 33% vs 66%.
FWIW, our simplification is to remove CON bonus from HP for everything (PCs and creatures alike). In general, this is roughly 75% (again, on average) of the listed hit point in stat blocks. I am using a sample of over 700 creatures for my analysis. However, at one point to really keep it simple, we just did half HP for creatures, and that worked as well.Combined with 5e increase in HP (I'm saying it is a 2x increase for simple math here - just as the "to-hit" rate is 2x higher) we find ourselves with the following question:
Would players rather have a 5e-style fight against a 100HP monster that can be hit 2/3 of the time OR a modded "old school"-style fight against a 50HP monster that can be hit 1/3 of the time?
It strikes me that players having their PCs hit 2/3 of the time is likely more fulfilling than missing 2/3 of the time. If we add the "more damage" assertion to the mix, we have the 5e-style fight resolving more quickly.
In doing the analysis with fewer HP but a decreased chance of hitting, the typically combat is extend about 1-2 rounds. Since a common complaint IME is combat is only 2-3 rounds and too quickly, this helps with that issue for those who have it.
As to the bolded comment, my experience is precisely the opposite. In old school, hitting was exciting because it did miss a lot. In 5E, attacking is even more dissatisfying because you hit so often it becomes routine:
"Oh, look, I hit (big surprise, huh?). Oh, look, I hit again... yawn
It really makes it more boring. Think about baseball. When a player gets a hit it is exciting, something is happening, because generally hitting percentage is 25-35% (or maybe that is on-base... or the same thing? I am not a baseball fan so perhaps I am wrong?). But, if hitting becomes almost expected, it loses its appeal.
When I was playing RAW at first, players were actually surprised and sort of happy when they missed! YMMV of course, but that is my experience.
Of course, we had to expand the critical hit zone, as it were, to keep it closer to 5% (1 in 20) instead of 1 in 400 with the "disadvantage" mechanic thrown in.
Missing was more common than hitting IME when playing B/X-BECMI and AD&D (1E and 2E). Granted in 2E, more things were added so hitting started to become more common, but even then I don't recall it getting over 50/50.Oversimplified? Most definitely. But, given these parameters, it strikes me as potentially adjusting HP and "to-hit" knobs down for no real benefit and, perhaps, added frustration at the table with 2x the misses. Is that really what "old school" was like? I honestly don't remember that - but, then again, it's been decades since I played in a 1e campaign, then I skipped 2-4, and started playing 5e exclusively 6 years ago.
Sure, like the other points it is just from my experience. I understand why 5E favors hitting over missing, because they want the players to feel like their characters are accomplishing something meaningful. But, with my house-rules, hitting becomes even more meaningful since it is less common and when you do hit, it counts for more due to the reduced HP.That said, I'd personally focus on incorporating other ideas from your list to give our 5e game a more "old school" feel, if that's what I was after for our table.
FWIW, since we've made these sorts of changes, no one in the tables I play at has shown or expressed any sort of frustration. When you keep in mind the numerous ways you can actually gain advantage, offsetting the "disadvantage" mechanic house-rule, you are then right back to the 60-65% hit. It has made things like flanking meaningful, without being over the top.
One final thought, the additional couple rounds per combat does NOT slow the game down. In fact, missing more often speeds it up. When you miss you have nothing to resolve-no damage to roll, no saves to make, or whatever. When you hit so often as in RAW, you are also adding the time to roll damage and finish any other things that arise. The game is actually faster IME so far by hitting less. In fact, hitting was so common that we decided to just use average damage for creatures most of the time (unless it would drop a PC to 0 hit points, in which case we rolled damage to give them a chance), and even some of the players adopted it for their own attacks.
It certainly might not be for most people, but I suggest trying it before dismissing it if anyone has interest in the concept.