MMO Design: Grinding vs Idleness

[Part of my MMO Design Folder]

When designing repetitive, daily content for casual players, how much time do you assume that casual players actually have to play?

That's one of the questions I would like to ask many MMO developers. For Cryptic's Neverwinter Online, I have to assume they went with one hour based on their latest content. If you count all the traveling, waiting for the daily targeted dragon and soloing the daily instance solo it comes out to around that much. If you group up you can cut that down a fair bit though. All except the traveling, and the waiting for the dragon.

I asked on chat what people actually do while idly standing around waiting for the timer to tick down. The responses were: read a book, watch anime, check the auction house tab, use the profession tab, play a different game in another window, and the most frequent answer: watch porn. Fair enough. For me though I find it to be bad design if you -want- to play a particular part of the game but can't because of some stupid thing like a 20 minute timer in your way. Even worse if the design actively makes people do stuff OUT of game.

I would change it so that instead of the timer, people simply had to kill the mobs in the area (to the tune of hundreds, like the old Ultima Online Champion Spawn altars) until a particular quota was met then out comes the dragon. The reward would then be based on not just how much damage you dealt / healed (allies) while the dragon was out but throughout the whole process, thus the guy who killed the hundreds of mobs but didn't get to land a hit on the dragon still gets a pretty good reward. This system will probably spit dragons out faster than the timer, but it will be "grindy".

Which do you think is better? Having players actively "grind" to get a boss to spawn or simply having a timer and a lot of down time?