Well I never made a MMORPG, Or an RPG for that matter... so I don't know.
I personally try to just break things down into manageable pieces, make frame works that can grow... I can edit, and move on...
trying to get a symphony of gears and cogs that churn ambiable - hopefully equating to an eventual "engine" to bring my ideas to life...
... but I'm on the same journey as many of you and I don't have all the answers but I can say it gets better... and worse... and better.... etc
so hang in and watch the creme rise to the top!
--Jason