If bioware makes this LFG tool for same server only, then even on some of the most populated servers would still have an incredibly long que time, especially DPS only players. I have a great community on my server, I love it. But a x-server LFG tool will not hurt it at all. I will still have the oppurtunity to join with members of my server. Using the current method of /gen spam.
Rift implemented a same server only LFG tool and it last only a few months before it went x-server, the wait for some classes/roles was just still too long. Why not skip the "save the community" speil, implement the x-server and those worried about thier "community" just don't have to use the tool. Pretty simple.