Hello there! Also, I must say I myself have left AD a few years ago for the similar reasons (though for me the biggest problem was the atmosphere and the overall community). For me switching to Sha’glade Cartel was the best possible decision, but the server definitely is not for everyone and so it’s wise to consider the good and the bad first.
So naturally, first the good things: RP-wise the server is a fraction of AD’s hectic RP, so you definitely won’t get overwhelmed (one of the most important reasons why I swapped–there’s only so much activity I can handle in a single second…). Since it’s so small, most highly coveted RP locations are empty and free to use during events and social. RP is mostly confined to guilds, as over the past two or so years walk-up social RP sort of fizzled out–however, as long as you join a good guild you will find yourself with plenty of RP as well as a potential for social! Last year some attempts begun to revitalize the realm with open RP (faction-reliant or neutral)–you can see the stuff we come up on the forums, as my friends and I post new events here quite regularly. Also, Horde RP is still considerably more active than the Alliance (although my Alliance friends are working on it 
).
The community of Sha’glade Cartel was very welcoming to me as I made the switch from AD, and I remain convinced in my view that it’s the friendliest RP community on EU, as the amount of edgelords truly is minimal here (I’ve been here since late WoD and I could count the amount of nastiness I’ve encountered on one hand).
Now, the bad things. The realm is small, and with that come the consequences, such as the fact that it means a small amount of roleplayers. While this results in a very close-knit community, it also means you won’t have nearly as much choice when it comes to RP. You don’t see griefers very often, but it’s no secret that the server is mostly populated by OOCers.
Since I mentioned the RP guilds, here are a few well-established guilds that offer fun RP (please read their threads and see where your character would fit best!):
They have all been around for a long time and have plenty of experienced roleplayers who are always happy to help a newbie out.
I hope Sha’glade Cartel becomes a virtual home for you, like it did for me! Good luck and I hope to see you around someday!