Six out of the seven classes are pretty good and enjoyable and unique. The Druid seems like it tries to be a hybrid of sorts but doesn't really stand out as being uniquely enjoyable compared to the classes he's derived from. Early on I think he had some viability issues with late game and PvP, and while maybe a lot of that has been fixed up, he's also simply not a lot of fun to play.
Summon Druids are annoying to play with if there's also a Necro in the group, as the Nec makes much better use of corpses than that stupid worm. Considering how much I used Necros in my time, I never liked to see a Druid.
Also consider that the Druid just doesn't look cool and his unique items are lame.
6. Amazon
My biggest issue with the Amazon is that I had an amazing one just before LOD, and I had a rare bow that was nearly as good as can be (just slightly off from the commonly duped/Ebayed one). PvP, Diablo runs, etc no problem for this gal. LOD comes out and my bow was pointless almost immediately. Without a good bow, the Bowazon isn't great, and it's hard to find great bows just by running around as a Bowazon. The Javazon was a big hit for running cows, and for the month that I couldn't stop running Secret Cow Level (it's amazing how dull an activity it sounds like, yet I was helplessly addicted to it), Javazon was great.
The Amazon is a good class. Pretty much everything on the list is a B+ or better aside from the Druid. I just hated feeling like I was really behind as a Bowazon until I had farmed up a good bow. Javazons were OK but a dime a dozen.
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Donny: Are they gonna hurt us, Walter? Walter: No, Donny. These men are cowards.
Haven't played one in a while, but these were fun for low level duels. Of course it also meant there was a time where you'd eventually have your Sewer run game streak ruined by someone going hostile with a low level Assassin and trimming down everyone who didn't take her seriously. Act 2 already had those narrow tunnels and lightning bugs, it really didn't need extra headaches for Hardcore mode!
The combat tree was a bit fun but not something I ever really enjoyed keeping up with for more than getting through Normal, but the traps are a blast. It makes for a common and cheap to use class, which is slightly boring, but at the same time you're not struggling if your weapon falls behind. Assassin specific items are pretty cool.
4. Paladin
Never really cared for the Paladin outside of PvP, but I had a blast with my Paladin in PvP circles. Auras were very nice, Zeal and Charge were fine, and of course the Hammer of Justice was pretty much *everything*. It was a dynamic little guy to play in duels, especially when I was in a group that ran 4v4 PvP matches all night long. If we're talking PvM, he might drop down to #6, and given that I don't really do any PvP, I'll probably avoid Paladins for good.
Melee Paladins are definitely gear dependent, but Hammerdin, sheesh, I loved my Pit running MF Hammerdin back in the day.
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Donny: Are they gonna hurt us, Walter? Walter: No, Donny. These men are cowards.
I love me a good Barbarian class, the big problem here is how gear dependent he is. If you don't luck out and find good weapons, you'll feel very underpowered. If you find something good, or have something good muled away, then the Barb is a blast. Early on, having a Barb meant you had to get a good drop or trade with people, which was fine, but it was just easier to grab a MF class and farm for your own stuff.
You then pretty much have stuff waiting for your barb, which detracts a bit from the experience of getting loot. Iron Man Barbarians could be intensely frustrating to play. There was also the issue of "what mastery do I pump up?" if you weren't muling over weapons.
That all said, Barbs were machines, WWing through everything, and I loved Frenzy builds nearly as much. Hell phys immunes definitely drag things down, and while Berserk gets the job done, it's no fun. But caving in everything else with a good piece of steel is just grand, and PvP was also a good time. A lot of WW duels just came down to "who hits WW at the perfect time" as well as pulling off perfect triangles, but group play was a bit different. You got your hands on other classes and they were often toast, but you had to figure out how to get there.
A classic and basic melee class (unless you try throw Barb), but still just an amazing romp.
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Donny: Are they gonna hurt us, Walter? Walter: No, Donny. These men are cowards.