Consider this! I play on Cerberus, and there's not much of a EU community anymore .. so during EU primetime we usually see 300-400 players online.
But every Tuesday evening I still manage to take 18(!) players for my Vagary LS event. How do I do it? I "interact" and advertise my events in advance. I have players who've done Vagary with me since the summer, and even though we have everything .. we do it anyways to get strangers their clears .. and to have fun.
While I would LOVE for Cerberus to be merged with a more active server (and I was asking about this back in 2011, so you're very late), it's not essential. The fun of it is working with the players we have, and while sometimes there's a lack of key jobs, we have fun trying the content anyways.
Also when you're selling currency items, the prices for bronze/bills/whiteshells and Alexandrites should be higher .. because there's less people to farm. So while there's some benefits to a more active server (not having to /yell for 1-2 hours to make a party), there's major drawbacks as well. The only thing I would like to see is more EU/NA players because we still see 500-800 during JP primetime. As for Dynamis, you can enter when you want, and if someone's in the zone .. exit and try somewhere else. Check the zone before you enter!
Also SE makes money from those jumping to Asura/Odin etc. Why would they risk losing players (and money) by merging servers when players will migrate anyways if they don't want to put in the effort to lead parties?
At this point a server merge would simply mean I have to /yell for less time. I would probably end up having too many players (and that still happens with my Vagary LS .. having to turn players away) and then I'll feel bad as I can only take 18 to an event .. or 6-10 players if it's Escha/Reisenjima. Make a few friends and enjoy the game as it's intended right now .. not how it was 5-10 years ago.