Returning Asking for Advice on servers/class

Hello guys! Played for a few years here back in 2008-2014 when the project was named differently. Recently I decided to return to this game and play it casually for pleasure. I am looking to play 70% PvE, 30% PvP on the WOTLK, but I see the server has a few different options. As I understand it, I have to choose between Frostmourne(dedicated PvE) and Icecrown servers. As I said, I dont want 100% PvE only, but I am afraid that on Icecrown it might be 100% PvP. Can somebody give me an advice what I should choose? I love doing dungeons, raids and such, in PvE, and I will probably do mostly battlegrounds in PvP since I no longer have active friends to play arenas with :( so sad... So, should I choose Icecrown server for my needs?

Second question: What class is in highest demand in PvE, especially in raids? I want to play mostly healer or dps in PvE, tanks are not my favourites but I can do it in dungeons I guess. The thing is, I want to choose a class that is the rarest. I dont want to be another Holy paladin for example, if theres tons of them. Back in the day when I played, resto shaman was probably the hardest healer to find, so right now im thinking either that, or a druid, or maaaaaybe a priest. So guys, tell me please, what do you think is the rarest PvE class out there that I should pick? My Priority is: Healing->DPS->Tanking

Thank you all, see you in-game. And... FOR THE HORDE!

Play on Icecrown, it suits your wishes best.

It isn't the rarest PvE class but take up Resto Sham. It'll be needed both in 10 and 25 man raids as a healer and RDPS so you're good on both fronts there.

thank you bro! Ready to hear more opinions if you guys have them! :)