I'm convinced you never actually did any heroic raids in WoW. 25 man ones were HARD. I mostly did 10 man and there was still little room for error. If someone died and couldn't be res'd you were typically screwed due to enrage timers.
I'm so glad I stopped playing FFXI way before that happened. My PLD would be a sad panda.
I think you have the right of it. I played FFXI through most of ToAU and while I was never heavily involved in endgame or in any super hardcore LS's, I think most of the "challenge" was in how long it took to do anything.
Fast forward to me starting WoW in TBC when SSC and TK were current content. The pacing of that game was so much different. (faster) Encounters were so much more mobile and you had to be very reactive to things going on. I played WoW up through the end of WotLK while tackling some of the hard mode raids (mostly 10 man, I never got in a guild that could handle 25 man) and I'd like to think that during my experience of playing that game that it has made me a better player in some regards.
Anyway, to contribute to the subject of the original post, I want the opposite. I want truly challenging fights, not campfests that take hours at a time. I just don't have the kind of time to play anymore like I did in FFXI. Boss fights should maybe be 30 minutes long TOPS for truly hard fights. The 10 minute fights I've found to be perfect for stuff like Ifrit, Garuda, etc. I don't want to do speed runs to get awarded extra equipment. (which it sounds like they're getting rid of) I'm not opposed to 3 hour long dungeons with multiple fights, but I also don't mind the shorter single encounter ones or the hour long ones.
I also want to know that I'm going to eventually be rewarded for my effort. Garuda was a good step in this direction awarding tokens with the chance of a weapon drop each fight. Ifrit and Moogle were just frustrating for me. I did Ifrit over 100 times and got a sword, axe and 3 cnj staves. While I know that's more than some people got, it's still ridiculous. I think I did Moogle a couple of times and didn't play anymore until the next major content patch because I wasn't going to go through that again.
I think if they can establish good systems for difficulty vs time-sink and a good loot system that rewards participation, the endgame should be something all players, hardcore and casual, can enjoy.