Here is the dirty fact of the 5 man dungeons, there has to be a boss that will drop gear for every single spec out there, the new loot drop process will eliminate the need for 30-40 bosses.
What do I mean? In MoP there had to be a boss that would drop every single specs gear, from Int to Strength gear, from cloth to plate gear, from crit gear to mastery gear. Every spec has a BiS that would gear them up for the next step in raiding.
Whats the new loot drop system in Wod? The boss will drop an armor type (cloth, leather, mail and plate) and the secondary stats will be randomized. That removes healing plate, tanking plate and dps plate and just requires that a boss drops plate. When you switch your spec the plate will switch its main stats to what your spec requires. When the boss drops plate the secondary stats will be randomized which will make doing the boss over and over again worthwhile as every time that plate drops for you it *might* be BiS secondary stats for you.
This new system eliminates the need for a boss to drop Crit strength plate, a boss to drop haste strength plate, a boss to drop dodge strength plate, a boss to drop haste Int plate. It requires that a boss drops a plate piece for every armor slot and the rest takes care of itself with spec changing stats or random secondary stats. (tertiary too.)
Thus no need for 40-50 5 man dungeon bosses, instead you can cover all the gear in 20-30 bosses. Sorry but thats what it all comes down to. The same people complaining that there won’t be enough dungeons are the same people complaining that they are bored and want WoD asap. The less they work on dungeons the faster you get WoD.
The good news is that unlike MoP they have recently promised that they will continue to add in more 5 man dungeons as the next expansion rolls forward.