Yes, Duty Finder pools players from Legacy and non-Legacy servers. Yoshi said in an interview somewhere that the top priority was the speed of the Duty Finder and that they aren't planning to change the combined pooling. I'll try to find the article.
I can't seem to find the article or thread where legacy players were discussed specifically. Maybe I read something about speed being a priority, and I imagined the rest. Yoshi did have a recent post that detailed everything else duty finder related though, but someone already posted it. So I'll link to that post, and I'll quote the section on speed priority.
Edited, Jul 20th 2013 10:07pm by CrazyLegzMcGee
■ Cross-World Matching ■
The main purpose of the duty finder is to "be able to experience party play immediately after logging into the game." In other words, the "matching speed" is a key factor of the feature.
Nowadays, people are generally very busy and don't have as much free time to play games as much as they used to. We would like our players to continue enjoying our MMORPG for a long time. In order to make that happen, we feel it’s important to provide an environment where the players always have something to do when they log into the game. It’s difficult for certain players to enjoy an MMORPG when it takes an hour to form a party (while there are some players that do have that free time).
I feel it’s important to "maximizing the demand." Therefore, instead of just matching players within one World, we have designed it so that players are able to match with players on the same data center. As an extreme example, with this system, even if there are only 500 players logged in per World (across 15 Worlds), that’s 7,500 players you can potentially be matched up with. Of course, the class ratio of the logged in players will have a huge impact on the matching system. However, we believe we will be able to avoid situations where a player is unable to enjoy the game because there are not enough players logged in when the play.
■ Matching Options ■
We received an inquiry regarding the implementation of the option to only match with players within the same World, but we currently do not have any plans to implement that option.
While I understand the idea of "How about we initially get matched up with players on the same World, and if that does not work out, match up with the other Worlds," this actually leads to a huge decrease in the matching frequency.
For example, let's say there are four players on the Worlds A, B, C, D, and these four players are wanting to defeat Ifrit.
Player A (TANK) selects the "Match with players in the same World" option.
Player B (DPS) selects the "Match with players on all Worlds" option.
Player C (DPS) selects the "Match with players on all Worlds" option.
Player D (Healer) selects the "Match with players in the same World" option.
Player A will enter the queue in the state of "Waiting for a DPS/DPS/Healer in the same World."
Player D will enter the queue in the state of "Waiting for a TANK/DPS/DPS in the same World."
Player B and C will enter the queue in the state of "Waiting for a TANK/DPS/Healer in all Worlds."
The problem is apparent right away. If all players were looking for matches in all Worlds, these four would immediately be grouped together to defeat Ifrit. However, due to this option, there’s a delay in the matching process.
While player A and D can switch to all Worlds if they do not find a match in the same World, every player has their own level of patience when it comes to waiting.
Let’s say player A waits for 5 minutes and player D waits for 7 minutes. In this case, all players will have to wait for 7 minutes until they are matched. During these 7 minutes, player B and C will wait while they wonder when they are going to be matched. Everything works out as long as these players are willing to wait, but let’s say player B gets tired of waiting and decides to join another party that was looking for an additional member via /shout, changes their role to a healer, or logs out. In this case, the match becomes invalid because one of the players decided to do something else.
Therefore, if it was just one player switching from one option to another, the only impact is making the remaining players wait. However, if every player has the option, it hugely decreases the matching frequency.
On the other hand, let's say we set the waiting limit of the matches to 5 minutes (automatically cancels if no match is found for 5 minutes) and prevent players for waiting for an extended period of time. Every player registers for the duty finder at different times, so unless the players registers at around the same time, they will never be matched up.
While my example was a little extreme, if this happened with all players or if the majority of the player selected "All Worlds," it would still decrease the matching frequency by a large amount as long as there are players selecting different options.
Of course after launch, we will take a look at the overall matching speed and the split between all the roles, and it's possible that we will do things such as ease up on the role restrictions and allow for multiple role requests (tank and DPS, for example).
However, the main thing we want to guarantee is that you can play in a party when you want to and create parties comfortably, and I feel that the most important thing is to see to it that this goal is accomplished.