GameHat, most of your complaints were fixed two or three patches ago.
1: Several good runewords are, in fact, available to casual players: Treachery, Spirit, Insight, Honor, Lore, and Black (the latter three having been around since 1.09 at least) all come to mind. These aren’t the best runewords possible, of course, but of course those are rarer. They’re still good enough to get you all the way through Hell.
2: There are two perfectly practical ways to complete sets. You can build up the pieces of low-level sets using your high-level characters and pass them on when you create new characters, or for high-level sets, you can trade with other players. Plus, of course, many set items are worthwhile in themselves, with the set bonuses being just gravy.
3: Any class with a means of disposing of corpses can take out Nihlathak without breaking a sweat. Assassins, druids, necromancers, or paladins should all be able to do it. Additionally, a barbarian or sorceress could just leap/teleport past all of his minions (who aren’t dangerous at all) and focus in on him alone. Or you could use any item that has the “slain monsters rest in piece” attribute. Or, of course, you could just skip him.
4: OK, this is a problem, in public games. The general solution is to play pub games for XP, and then only with your friends or solo when you’re looking to get loot. There are a large number of folks from this board who play (or at least, who probably will play, if there’s a new patch and ladder), and we all share loot fairly (like, if a good wand drops, the necromancer in the group gets it, and so on).
5: Hostility can only be declared in town, so you already have time to leave the game if someone hostiles you. Anyone who’s using a hack to get around the only-in-town restriction would probably also hack around a 10-second timer.
6: I’ve never had a problem with trap assassins late game: They can dish out just as much damage per time as a sorceress, in a larger area, and they’re more tolerant than most of lag. This has been the case since at least 1.10, when synergies were introduced.
7: OK, this one I’ll grant you. There are other good bows than Windforce available now, but they’re all expensive, which doesn’t change the core of the complaint.
8: With one solitary exception that I gather from your other complaints you’ve never seen, it’s impossible for any monster to have more than two immunities. Even if a boss spawns with attributes that would ordinarily give it more than two immunities, any extra immunities are dropped.
9: Gambling uniques and sets is possible, albeit unlikely. It’s also possible to gamble up rare items that are better than any unique, in some cases.
10: Some of the best items possible can only be produced by those “middling cube recipes” you mention.
11: I don’t know what the issue is here. Sure, the servers occasionally crash, but when they do, all characters that were on that server get rolled back so you don’t lose anything.
12: OK, that’s annoying, but as magnusblitz mentioned, they’re not really deleted.
13: How would you even find yourself on a ladder that size?
14-15: I don’t PVP, so I can’t comment on these.