The term "casual" has a really weird definition according to this game. Cascual is 100-350 hours. Hardcore is more than that. The game is designed for hardcore, and since that's outside of what most players can even manage, they just resort to bots.
I also don't remember having to spend that much time in d2 to get the best gears for my characters. I spent a lot of time making multiple characters, and doing stuff with those characters - not just gearing up a single character to a near impossible goal.
The game is designed for hardest of hardcore players. Most people are "casual" according to the current design of the game, as lots of people - and it's not hard to find them, they posted in this thread - don't consider 350+ hours of playtime to be hardcore.
Blizzard did a good job designing a game for the masses for normal through hell difficulties, but then they completely made the inferno grind to be the most hardcore ever.
Someone accused me of complaining about the grind in a grinding type of game, but that's just a non-sense comment. You shouldn't have to spend so much crazy hours just to get a reasonable upgrade to your character in a single item slot, nevermind the rest of it. It does feel like a job, as you said. It's taken to such extreme proportions. It was never this difficulty to get the best items in d2.
To be honest, while they lowered drops and widened the quality of the gear that drops, they did in the hopes of people not realizing that there would be nothing at all to do once they eventually spent the 1000+ hours and got there. What is there to do with him once you attained it? Show it off? That's it?
In D2, it was easier to assemble the best characters, but then you spent dozens of hours enjoying them by actually doing stuff.