I'll start out impartial by listing out the pros and cons of both lockouts and % based drop rates then move onto my personal opinion.
(To avoid confusion, by % based drop rates I mean for example 5% 10% 15% ect per chest to get a piece of gear per run)
Lockout Pros:
Extends content by preventing you from getting too much too fast
Creates tight "static" communities
Helps curb the competitive difference between casual and hardcore
Lockout Cons:
Content extension is artificial
Prevents larger groups from playing together
Creates a curb between the lucky and unlucky
Percentage based Pros:
Extends content by making you have to play more to get more
Large groups can play together freely
Allows players to enjoy new content without restriction
Percentage based Cons:
Creates a gap between those with a lot of time and those with little time to play
Makes players run the same thing several times to get gear
Makes older content less relevant (Why farm mythos when you can farm <insert-high-level-content>)
Personally looking over the top 3 pros and cons of both systems I lean more towards % based drop rates. I don't mean anything extreme, however. I personally think 2 Chests with 1% lowest or 10% highest for an item is a good balance. (Now onto my anecdotes)
With that said I think the effects on the community would be game changing. People would become more social because running outside of your current static (FC or not) would become more common place and that would foster more friendships between people. This from what I saw in 1.0 creates a stronger community that makes the game just that much harder to unsubscribe from which would just be good for business.
On the other hand there is a negative effect I can't stop seeing on the community that has been because of lockouts. Small statics have caused a lot of xenophobia between players. People get very unfriendly with people outside of their statics even within a FC. Also I see a lot of people getting so left out from their FC because of statics not letting them in that they end up leaving the game over it.
I really do hope the devs try to use % based drop rate in dungeons instead of lockouts in the future and if a community rep relays this or has relayed similar feedback to the dev team I would absolutely be thrilled to know about it as well.
Anyways, those are my thoughts but I would love to hear others' pro/con lists and thoughts as it would benefit to hear from other players not just myself. (But please keep it civil!)
EDIT:
These to me are some replies that really stood out to me here so I'm replying here on the OP to advance the subject.
This is a common issue I hear about, and I hear about it often as well as experience it. It's one of the biggest drawbacks of locking out players from participating instead of a CT style lockout or % based.
That is indeed a good argument for lockouts and it does make me think - since Coil 1-5 were unlocked I did next to nothing but farm it. I just had no time for anything else.
A Crystal Tower style lockout in my opinion would be really beneficial to the community and would effectively foster the same kind of "Play with my friends and FC" as RNG drop rates without the much hated frustration of low drop rates. I feel it would kill some of the fun of getting a drop, but that's opinion.
I never played XI but I do hear a lot about the diversity of content it had in it's prime. I'm hoping FFXIV gets the same treatment where we will not be limited to 1 set of highest tier armor and 1 way to get it. To me this is the best outcome as it makes (almost) everyone happy.