We didn't have cross-world party finder until nearly the end of the expansion, so we had to be on an active "raid server" to find any parties in Party Finder.
We didn't have [Duty Complete], so we had to put "2 chests, no bonus" to scare away people who hadn't cleared. It looked toxic and put significant amounts of people off raiding. [Practice] parties just put "learning party".
Raid free companies that put statics together were more of a thing then, but now these aren't needed as much because we can form cross-world or cross-data center statics using discord servers and cross-world linkshells.
Paladins couldn't block magic, so many of their abilities were useless against the magic bosses we were facing. We had to face targets to block their attacks or auto-attack them. Parry was a stat that provided RNG mitigation, which means the mitigation would probably not be there when we needed it (against tank busters) and it didn't work against magic either. There were attacks on tanks that relied on parry to proc which made it even worse. We cried out for % damage reduction stat to replace it and we got it (Tenacity) in the next expansion, but people still don't care for the extra mitigation it provides.
Warriors' Raw Intuition would parry from the front and crit them from behind. To nullify crits, Awareness was always cross-classed and combined with Raw Intuition. But parry is parry which also only worked against physical attacks. A lot of the changes since have homogenized the mitigation because we would criticize it when they had significant differences like this.
We still had to reach an Accuracy cap so our attacks wouldn't miss. The developers were aware it added an extra annoying step to do raids, so it changed to Direct Hit in the next expansion.
We had to level other classes for basic abilities we wanted to cross-class, such as Provoke or Second Wind. We cried out for this to be changed somehow and we got Role Actions in the next expansion.
Everyone will tell you this, but Machinist and Bards had cast times causing a lot of Bards to quit the game. Nobody played them anymore, so the cast times were removed in the next expansion where the number of Bards exploded again.
The hardest Alliance Raid I ever remember was Weeping City, which everyone dubbed "Wiping City". The first boss had gazes, sticky web placement and DPS checks that became irrelevant the next time our item level increased. Although rare I did see wipes to it. The second boss was very difficult for people because they didn't kill adds or stood in their death aoes. They didn't prioritize the correct add in the transition phase (which is an easy dps check now) and they didn't understand the mechanics after it either. The healer check would wipe sometimes as well.
If they got through that, they had to fight Ozma. Ozma would frequently cause parties to abandon or people to leave in frustration (but their replacements allowed us to clear, so they were in fact the problem). Now, we skip to the transition phase too fast and if the second phase starts wiping, we kill it too quickly or survive easier because of item level.
I've seen people say that alliance raids after that were hard, but that hasn't been my experience. There were people who would abandon the first boss of Dun Scaith, but they were just impatient and the boss would usually be defeated. The last boss would wipe sometimes but it had a checkpoint. The last part with the orb mechanic would wipe parties but the boss began to kill itself as well, so we just had to survive. These mechanics are mostly intact today because we sync to the final tier item level.
I did Steps of Faith shortly after Heavensward released and it was easy. While someone would try to order people to certain tasks, I (and most other people) saw this as irrelevant and just killed the boss. Killing the boss worked as long as the tank mitigated and picked up the adds and the DPS threw some aoes on them. Healers needed to be ontop of the healing, but if not, we could release and sprint back.