EQ did a very good job creating an all around need for every class. While some not as popular as others, the content was designed around those numbers as well. Buffs, crowd controls, debuffs, etc.
Our guild was a very fast paced, stay alert type. Paladins and SKs were extremely important for clearing trash, Kiting, OTing and had to stay sharp during the main events. While we primarily used Warrior rotations on main mobs, the SKs and Paladins were durable and had their roles. It was also dependent on the user too. I've met some Warriors in my days that weren't worth a shit. You could put them in the best gear and they still couldn't keep agro on multiple or even single mobs. They would break mezz, or all around just didn't have a clue about the mechanics of the content.
For grouping, we had a group within our guild that consisted of a Paladin tank during exp/quest times, and I would put him up against a pickup warrior any day.
The diversity in the classes was much more drastic than today, but so was the design of the content. Unfortunately, there is a relatively small group of people left from the 'glory days,' that grew up on these game mechanics. The demographic has changed and if SOE wants to draw subscribers, they're most likely going to have to stick with what the new generation is accustomed to.