Tailoring a dungeon to the group make up seems weak. As previously mentioned "KAY lets all roll full pyro and AOE AOE AOE AOE cool loots bro". Part of the challenge of dungeons is to figure out what you need to overcome all the different challenges. Rift is the first MMO to really give us such strong adaptation tools on the fly. So while the dungeon wont change to the player the player will **** well be changing to the dungeon.
NOW!! back to the OP. Some favorite dungeons of old include:
1. Lower Guk- eq classic holy sweet mother mary nothing trains like guk nothing spawns through walls like guk and nothing gets lost like guk. If you havnt played this dungeon go make an insta 60 on some emulator and run it, the epitomy of dungeon.
2. Great Barrows in Lotro- Really cool feel and atmosphere, semi challenging mobs, good time all round.
3. Scarlett Monastary- WoW had a lot of fun in all parts of it, the lore the mobs and the lewtz were great, a blast the first few times threw.
4. Im just gonna list a bunch of good ol classic eq dungeons... Befallen, Splitpaw, SoldungB, najeena, man that game was full of good Dungeon crawls, lets hope Rift can do it big.