Fates literally do not scale.

[Riderpride]

Agreed with Wiggles. There'd be a lot of coding, and a lot of potential issues/exploits/griefing cropping up if FATE's scaled based on the number of players that joined in. Especially if you want them to scale on the fly as players join/leave the fate "zone" as it were. If it didn't scale as players join/leave, there could be easy exploits by having one player hit the FATE, mobs pop up based on 1 player in the FATE, 30+ people jump in to try and get credit, can't, now just wasted their time while the initial player reaps all the rewards for just being there. The other alternative is if FATE groups are roaming around, the opposite happens. 30+ players roaming the countryside looking to isolate players, as a FATE pops up, mobs spawn for 30+ players, those same 30+ leave the one player to fend for himself, likely getting killed in the process, thus griefing.

[Jynxii]

Stuff.

I'm sure they can have some 'smart' coding to address these issue. As was mentioned above, they were able to do it perfectly fine for Guild Wars 2, so can you (or anyone) tell me the exact difference between a) GW2's open MMO world and dynamic event system and b) FFXIV's open MMO world and FATE system?

You could program something that would have an equation like (Zone population /2) and base the scale on that, and then 3 minutes into the FATE's life have a second check to determine the amount of players within boundaries of the FATE (plus a little more), and then scale up or down depending on that. There is no amount of logic that should say it is okay for a 30 minute FATE like "Keeping the Hive" to be done in 90 seconds, let alone be done at the spawn point and completely ignore the 'defense' mechanic. Dynamically scaling stats is nothing new; games of the ARPG (Diablo/Torchlight) do it all the time.

Also, in response to your comment about the first one getting there, and the rest having no chance; As it is already, if you (and your group) aren't there in the first 30 seconds of the FATE's life, your shot at scoring anything more than a silver is near impossible, and sometimes even a silver is near impossible.

In regards to the character limit (which is painful), you can just cut a large section from the bottom of you post, hit the post reply button, then edit and paste the last section in.

[skiwi]

*Snip* because of character limit

Your ideas sound feasible and I think they are, but keep one thing in mind, you asked "so can you (or anyone) tell me the exact difference between a) GW2's open MMO world and dynamic event system and b) FFXIV's open MMO world and FATE system?".

Yoshi-P has stated this quite a few times, they have a very different server setup compared to any other MMORPG last seen. Their server handles practically everything, I am not saying that it is a factor that could worsen the idea of scaling, but it is definately something that they need to take into account and they could, because of that, not 'copy-paste'* code from GW2 in FFXIV:ARR.
* Of course copy-pasting is not possibly like this in software, but it's just there for the argument.