Europa, Catskills and Atlantic are probably the top 3 largest role-playing shards at the moment, followed by Chesapeake and Baja.
T.F. is currently the largest roleplaying guild on Pacific, we have 3 Pacific roleplaying forums, including the one I opened recently. ElF, SAGE, RSB and other older RP guilds have recently vanished. EOTD (The Wendol) is part roleplaying. I run 2 roleplaying guilds, The Guardsmen Militia a human guardsmen guild rebellion guild and I run the Bloodraven Clan which is a orc guild. I am trying to start up RP-Warring as well between multiple guilds, if you wish to know more and want to get involved, just drop me a PM.. Pacific is not dead when it comes to role-playing but it certainly does not have the most role-playing. For the most imersive role-playing and the most realistic hands down, I would go for Europa, they have a low-fantasy setting type of role-playing, and it is a beautifully made shard. I don't play there cause of my high ping, so I normally stick to Pacific. Each shard seems to have their own type of thing going on when it comes to RP, like their own theme.
Duke Winter could tell you more when it comes to Pacific.