A little background: I came from a mid-tier WoW guild. I think we finished everything on Heroic but Lich King in WOTLK. We're good enough to get a few heroics down each content cycle and push our way through the rest in cleanup after the next cycle starts. We typically have no issues breezing through normal modes with only Nefarian normal in Cata and LK normal in WOTLK really being couple week toe-stubs. We're the definition of the casualcore I think.
I found EV normal to be way too easy when I was thinking of it as WoW normal; then they renamed it Story Mode so I'm good with it. That makes Hardmode in TOR the equivalent of Normal in WoW. After sloughing through TBC, WOTLK, and Cata raid content (I quit WoW during Firelands progression), I gotta say TOR's hardmode was way too easy. I think we finished all but Soa in one night and after 1-2 tries at most on a boss. While normals in WoW do drop fast, we'd never had them drop that fast. This was 8m mind you; I hear 16m is more in line with that level of challenge (we were 25m in WoW). Nightmare mode which I would say is Heroic mode in WoW also dropped and we were like 6/10 in a matter of one 3 hour session. Its pretty easy.
I think the health of the game would be vastly improved if they adopted a similar approach as Blizzard (although with more of a gradual curve in Nightmare difficulty - Blizzard has a tendency to do a "You can destroy normal mode, but can't kill the first boss of Heroic" approach). It cannot be denied that TBC was the time during the most WoW growth and raids were squarely aimed at the hardcore elitists and the "casuals" aimed at that and strived to it. You need to please both to keep great word of mouth going and grow the game. You want both customers and I think harder nightmare and hardmodes while maintaining the tuning of Story mode is the approach they should take. The other thing that needs to happen is Nightmare needs the best gear. I clearly never got the best gear in WoW being a mid-tier guild, but we did well enough. Reward the difficulties appropriately and the base will grow.