I have a proposal for a type of server which should both satisfy those wanting something as pervasively difficult as classic was in PVE, as well as providing an even more group-oriented MMO experience.
Premises -
Using 1.12 actual gamestate for comparisons.
Most adjustments from whatever goes live as 'classic' would be spreadsheet based in mob health/dmg, as well as some quest adjustments (group to raid). possible adjustment to earn xp for raid mobs while in a raid.
Premise - make most or all outdoor mobs elite, most outdoor questing group-oriented, and extant group quests become small raids (a la Darrowshire or Nathanos)
Suggestions -
1) outdoor normal mobs become elite. tuned to have ?? 2x-3x health and general damage, so that a player alone 1v1, blowing all cooldowns, MIGHT kill one before dying. Assume what are now outdoor normal mobs are tuned for 3 player groups, 2 dps (1 could be a tank or not) and 1 healer. This would in effect make the 'hardcore' servers a group game in most leveling content. Adjust certain item-drop quests (8 bear heads etc) to not require 3x the kills on average.
note that some areas with tightly packed mobs (troggs in loch modan) would in effecft need 5 players and even then might be ruff going, just due to mob density.
there are some mobs with powerful abilities (defias pillagers for example) which obviously would require some thought on how to buff, or they start one-shotting players. We can assume this is something that would be dealt with.
2) outdoor elite areas become raid areas. quests for these areas become raid quests. tune around 10-man raid size?
2a) need to consider whether to allow xp from raids, even if it is a very low xp rate. maybe have raid-mobs give xp in raids, but not non-raid mobs.
3) increase required xp/level (or decrease xp/mob gain rate) to require substantially more work for a level. This will require clearing more leveling zones, and more dungeons.
4) consider which dungeons may be viable to re-tune as 10 or 15--man dungeons. this is the 'work' part for blizzard as would require re-tuning work. consider 2a) above too.
5) extant 'raid' dungeons could, if game area space permits, be retuned as larger groups, 20? UBRS, Strath, etc.
6) actual end-game raids - a single difficulty tuned to be nose-bleed hard.
A number of effects lead off from this -
1) healer and tank specs are NEEDED in outdoor questing, and it is possible to level outdoor questing in those specs.
2) much more social game.
3) with the xp changes, leveling can last months or longer just on a single character. players will complete most questlines for their faction.
forseen problems -
1) need more quests at higher levels. there are several zones that seem quest-poor - Azshara, Blasted Lands, plus there are several 'undeveloped' zones in the classic map that, if developed (and I think they could just be pasted in from the retail map, with some trimming, Hyjal and twilight highlands, for example) which might make up for this.
2) need people in zone to level. I think if left to itself this problem fixes itself via world channels, similar to how finding groups for dungeons is, but less structured and a much smaller up-front time committment required. Give people social tools and let them figure it out.
also, there are later instanced areas (grim batol for one, and the new blackrock area from cataclysm) which could be re-purposed and propertly tuned for this content.