Thanks for the tip! I'll probably give the necro a shot soon (maybe tonight? I pretty much both IIDX'd and VR'd myself out by this point). I remember why I never tried it: my friend always played necro, and we didn't see the point in rolling two of the same class. Guess I just sort of stuck with that mentality long after high school, haha.
The main reason Diablo 3 needed to ratchet up the difficulty the way they did is because every last ounce of gear synergy in that game was artificial. The way they implemented sets is completely fucking busted, and basically forces you to build your character a certain way in order for them to be even remotely effective. The damage scaling is so out of whack that simply attaining the 6-set Firebird's Finery wizard set is enough to bring you from having a rough time with T4 to annihilating T8, and a few more pieces will easily push you immediately to T10 and beyond. I guess it's kind of entertaining in a mindless sort of way, but it kind of took away any freedom of choice and staying power. Whenever you check the ladder, the top 200+ people all have the exact same gear and skills. I hate it.
It's not to say that Diablo 3 was great at launch. They tried to stick with D2-style progression, but their RMAH-supporting overly random loot system and drastically reduced level of gear customization absolutely wrecked the game (much the same way as how removing grenades killed a major strategic aspect of TeamFortress, IMO). Their fix for that was basically copying WoW's itemization model, which...doesn't really fit ARPGs.
In Diablo 2, it doesn't feel like they even attempted to force synergy, and if they did they did a damned good job of hiding it. It almost feels like they took the sandbox approach, threw a bunch of toys in the sand, and let people play around with them to their heart's content as god intended. Sure, it's a little clunky and rough in places, but the general approach that they took was a reasonable one. There's randomness, sure, but it's far less prominent. D3 has always been ruled by gear, while D2 is more about what you do with what you pick up, and given the success of PoE, GD, and the fact that Diablo 2 still has a decent player base, that's definitely the approach that people prefer.
Hopefully Diablo 4 ends up landing somewhere in the middle. From what I've seen they're putting more of a focus on action-based movement, but I don't think that's necessarily a bad thing. Diablo 3 sort of tried to do that in a sense but it wasn't bold enough to go all the way, and every instance of it attempting any sort of difficulty always proved to be more of a gear check than a skill check (*cough cough* fucking Inferno *cough* Torment 13 *cough cough*). If D4 rolls back itemization and allows people to actually build their own characters again rather than railroading them down a set path, it might very well be something I get into. We'll see, I suppose.
Edit: Started my necro and managed to find a wand that gave me +2 skeleton mastery within the first five minutes. Not too shabby! Gotta admit, it felt pretty awesome to just sit back, relax, and watch 5 skeletons tear Blood Raven to shreds.