Well, Udawg that's a "tad" extreme
In wow the timers are set to a week or so and you get a respawn of the dungeon.
In EQ/Vanguard style open dungeons, the dungeon repops quickly so that you can do it over again quickly and the bosses repop every couple of days. This translates into a guild conceivably being able to do said dungeon more often.
Now I know you say that you have to compete with other guilds and that's where community building comes into play. The leaders of the guilds actually powerful enough to "do" a certain dungeon will coopertate and set up a server rotation for them and may even team up to co-op the dungeons in an effort to learn how to do it.
You will say that instances mean you don't have to bother with that and there there are no limits on who can try the dungeon but I've never seen too many issues with guilds not being willing to give another guild a shot at the boss. If the new guild fails, then the boss is still there so the established guild has lost nothing.
Then you have to factor in the sheer number of dungeons. Compare how many VG has now in it's early state to what WoW has now and I'm pretty sure VG already has more total.
That's how Sigil/Verant/SOE get around the **** blocking is by having MANY dungeons available to do so that while one guild is working one, the other guilds can work the others and this rotation works! It's been proven 100%.
There's ups and downs depending on how you choose to look at each approach.
Is the glass half full or empty?