The information presented in these archived FotDs is now outdated, but that's often the most interesting thing about them, seeing how much the game has changed from then to now.
The original FotDs are indented and italicized. Explanatory comments below them were written by Flux at the time the FotDs were archived, usually a couple/few months after the original FotDs had been presented.
June 1, 1999
- Traveling around the surface of each Act in Diablo II, your character will traverse a vastly larger area than the small town of Tristram covered in Diablo. To make this process fun and quick, there are several new features implemented, such as running, (which does not exhaust your stamina while in town) and also Waypoints. These can teleport you from one Waypoint to another one in the same act, providing you have already located it on foot.
Waypoints were just recently revealed at this time, after there being hints of ways to travel quickly around an Act, but never any concrete details.
June 2, 1999
Interesting detail here, that initially some skills were only going to allow a single point, perhaps to keep them from being over powered. Unknown how far Blizzard pursued this angle, they might have just toyed with the idea, but it got out in some preview and became accepted fact by fans, when it was never really a permanent idea by Blizzard.
June 3, 1999
- Keys are a new feature in Diablo II. They were debuted at E3, with some surprise to the people who were first finding them. Monsters dropped them and NPC's sold them for a reasonable price. The only things that were locked in the E3 build were an occasional chest, and it was like Gauntlet, every key fit every chest, and once you used the key, it was gone. I got the feeling that keys were a new addition, and that they would be expanded a lot in the game, probably to include locked doors or other things, and also more than one kind of key.
Keys weren't expanded any more, though there were plans for them to be more involved. Lots of cool ideas never get fully-developed just due to time constraints.
June 5, 1999
- Range is a much more interesting aspect in Diablo II. All melee weapons will have somewhat different range, with polearms effective at a greater distance than clubs, and clubs having more reach than a dagger, and so on. Throwing items, like potions and knives, travel in an arc to the spot you target, and arrows go to just past the edge of the visible screen, while thrown Poison Javelins, (at least at E3) would continue for several screens, leaving a contrail of green gas you could chase them by.
Range was tweaked a lot in game development, especially on ranged attacks, such as how far spells would travel, how far off the screen arrows or javelins would hit things, etc. In Diablo all melee weapons had the same range (equivalent to 1 in D2) but arrows and spells had basically infinite range, though they suffered a major AR drop at greater distances. So having things not go until they hit a wall was a major change in D2, as was being able to hit something with a melee attack that you weren't right next to.
June 7, 1999
- There will be a worldwide Battle.net ranking system for Arena Games in Diablo II. Exactly how it will function is as of yet undetermined, but separate ladders for each class are confirmed, and there will be a variety of different area tile sets, and also the ability to wager an item with your opponent before the duel, with the winner getting it. Currently the plan is for characters to not drop any equipment when they die in the arena, and many more features of Arenas will be announced soon, and then tested extensively during the beta.
Pity Arenas didn't make the final cut, they would certainly have made PvP more fun than the typical FFA Blood Moor duels we see today.
June 12, 1999
Early on some masteries, the Sorceress' at least, were only going to allow one point in them, so just on or off. Others would probably have had hard caps at various numbers, rather than all being 20. There was also much wondering early on how we'd tell an axe from a polearm, or a dagger from a sword, etc. It wasn't yet known that weapons would have that info in their hover description.
June 14, 1999
Another tidbit long forgotten. Town Portals vanishing after a set time? That seems like it would be pretty annoying, and of no real benefit, so you can see why Blizzard removed that concept from them. The hover info on where a portal went to was a real breakthrough, you didn't see that in D1.
Another change in D2 is that portals open where you are standing. In D1 they could be cast anywhere, even over walls, and were easy to trap therefore.
June 25, 1999
- Palette swapping (monsters with identical graphics and different colors) returns in Diablo II, though to a lesser extent than it was used in Diablo. No more are there 4 or 5 different colored versions of every monster. In Diablo II, (at least this is how it looked at E3 in May, which is not at all the final version of the game) there is some palette-swapping, but mostly for the same type of monster in different acts (which also generally have different names). Also, this works in concert with the component system, where monsters will have different weapons and armor, as opposed to the identical demons you saw in Diablo. And of course they will have different strengths and resistances as well.
The monsters in Diablo II still do a lot of palette swapping, but not as much as in D1, where there were 3 or 4 or 5 different colors of each type monster, with no other graphical differences. The color changes are better done in D2 also, paired with different weapons and heads and textures and such.
June 27, 1999
- Herbs are a new feature of Diablo II. They work something like potions or scrolls, in that you consume them with the use, but they provide a (usually) temporary boost to some attribute or aspect of your character. They were still a recent addition to the game when we saw them at E3, but such effects as boosted fire resistance, increased stamina, and faster attack are examples of the numerous herbal boosts you can expect to see in Diablo II.
Herbs went the way of reagents, gone over time. Some herb effects popped up on shrines, and others in the thawing and cure potions NPCs sell. Blizzard found that herbs were either too powerful, or too weak. If they were really good, players would horde them and make themselves fireproof for a hard area, or give themselves super fast attacks to slaughter a boss. And if the herb effects were nerfed, then no one used them at all.
Charms were added much later in development and these helped with character customization beyond what could be achieved on equipment, and that's a sort of herb-like effect, though it's not temporary.
June 29, 1999
Dual wielding was a very cool new idea when announced for the Barbarian, though it had been previewed by the Bard hidden character in Diablo I's expansion pack, Hellfire.