In Delving Deeper, fighters have a number of attacks against "normal-types" (of 3HD or fewer) equal to their own HD. I don't recall reading anything like this in OD&D, so would you please describe where it comes from?
I should start by clarifying a couple of things:
Firstly, DD defines "normal-types" as having fewer than 3 HD. So a 3 HD wight is heroic, as is a 3rd level (3 HD) fighter -- and this early entry into the heroic tier is a real advantage of the fighting class as heroic-types are no longer subject to multiple attacks vs. normals.
And secondly, DD talks in terms of numbers of attack rolls rather than numbers of attacks because, when we're dealing with one minute combat turns, an attack roll can be representative of more than just one attack; even when you're rolling more than one attack roll per turn.
Getting back to the question, the multiple attack rolls rule is described in three OD&D sources; Chainmail (especially page 30), Monsters & Treasure (page 5), and The Strategic Review vol 1.2 (page 3).
Monsters & Treasure talks specifically about monsters having one roll as a normal-type per hit die, and cites a 6 HD Troll as having six rolls versus normals.
That's monsters, but what about the players? For the fighter-types we know that Chainmail ascribes multiple attack rolls versus normals to heroes and superheroes, and that OD&D is built right over this. Chainmail heroes have four attack rolls and OD&D heroes have 4 HD. Chainmail superheroes have eight attack rolls, and OD&D superheroes have 8 HD. It seems to fit very neatly with the rule in M&T.
Then we have EGG's article "Questions Most Frequently Asked About Dungeons & Dragons Rules" (appearing in The Strategic Review vol 1.2, page 3) which explains in detail that an OD&D hero has four attack rolls versus normal-types. It's notable that EGG overrides his earlier rules in the FAQ example by having the hero throw four attack rolls as a hero rather than as a normal-type, but DD ignores this in favour of the earlier rules which, in my mind, work a lot better.
Regarding the possibility of multiple attack rolls for the non-fighter classes, a Chainmail wizard has two attack rolls versus normals but an OD&D wizard has 8 HD, so it isn't quite so clear cut for wizards as it is for fighters. The FAQ article doesn't discuss multiple attack rolls for non-fighters, so all we really have is speculation that an enemy cleric or magic-user might be treated as a monster, and might therefore have one attack roll per hit die versus normals. DD leaves this option open to interpretation, just like the original.
Personally, I love the Delving Deeper thief and its use of d6s rather than percentile dice. What was the inspiration to use the 4-in-6 d6 rolls that stay flat across all levels? Did you anticipate any pushback from players not used to their characters not improving in those things?
The main inspiration for the d6 based thief skills was the 3LBBs' general treatment of similar dungeoneering feats. The manner in which elves are good at locating secret doors, in particular, was the model for the DD thief's skills.
The addition of the official percentile-based skills mechanic is frequently quoted as a pivotal shift in game design -- a shift away from the simpler mechanics of the 3LBBs, and toward a more complicated system (one where knowledge of a thief's odds begin to reside more with the player, and less with the referee).
So all I did with the DD thief was to suppose that this pivotal design decision was yet to be made. So, in lieu of a percentile-based skills system "yet to be invented," DD simply employs OD&D's pre-existing mechanism.
Regarding push back from players, I don't think I've heard anything unexpected. It was a design goal that the DD thief should be easy to be house ruled, so I was actually pretty pleased when, right away, I saw a bunch of guys discussing how they were planning to house rule their thief class. If nothing else, DD had encouraged people to start hacking out their own thieves. I thought that was pretty cool.
Sure, a number of folks suggested mechanisms for a DD thief's skills to advance with experience -- and that's all great discussion. My observation is that systems of advancing mastery generally go hand-in-hand with increasing difficulty, so the dilemma is then whether the additional load of another system really adds much to play. Maybe it does for some.
But even as simple as it is right out of the box, I reckon the DD thief addresses a couple of issues with the Greyhawk thief. Namely, the DD thief doesn't have terrible odds of performing his primary function at low levels (so he can "thief" right away), he doesn't achieve infallible skills at high levels (so he remains interesting to play), and you don't need to muck around with all those fiddly "skills" on your character sheet. I'm not saying it's perfect, but it works okay for me.I'm already on record as being a huge fan of DD's thief. Thieves are one of those contentious issues in the OD&D community. For example, Simon himself suggested that my inquiry here might be begging the question "Why include thieves at all?" I'm not going to take things quite that far, but I do think that DD tackles the "self-justifying thief" concept quite well with the thief's level of ability from the outset and lack of improvement. While calling out some examples of the sorts of tasks that thieves might be good at, the text shies away from explicitly saying "these are the thief skills." To me, this side-steps the "self-justifying thief" problem (if you don't know how this argument goes, here's a bunch of Google hits on the search "self-justifying thief rpg" including one on this site) by not specifically calling out "thief skills" and not having such a steep improvement curve. I'd like to suggest that the improvement curve implies the natural problem with the "self-justifying thief" in that thieves should never be worse than a non-thief at thiefy stuff, and if thief skills are crazy low and get much better over time, then your ordinary person would have to be even less likely to accomplish these tasks. Delving Deeper tackles the problem from a different angle. Instead, attention is given to the chance a normal person might have to accomplish the thing (based on the existing probabilities from the OD&D RAW) and then extrapolates the thief's probability of doing the same thing given his superior training in that field. The lack of improvement here is sort of icing on the cake: the thief is really good at this stuff from the outset (making up for many of his shortcomings in things like attack progression and HD) and gradually improves elsewhere, so why do the thief skills need to improve?
While I'm here, I might as well say a thing or two about Simon's reasoning behind the fighter, right? The thing that strikes me as neat is that, by using the OD&D/Chainmail rubric of when characters get multiple attack rolls and how many they get, Simon has eliminated the need for the clunky, wonky tables of other editions and made everything follow one streamlined system. In earlier editions of DD, fighters buck this trend, being able to "[throw] one attack roll per round for each of his own hit dice," which conceivably could begin as early as level 2. When I asked Simon this question, I hadn't really noticed the exclusion of this line from the fighter class write up, or even really the changes in language ("normal type," "heroic type," etc.) that Simon made in an effort to clear up more than a few things. I really liked the original rule, and keep that alive as a house rule in my Hyperbarbaria game as an option for fighters only.
Speaking of house ruling, next time, we'll take a look at house rules in DD and the house rules that Simon himself uses in his game(s).