They have been buffed, shields can take more damage before disappearing and heals have been buffed slightly, making it a more viable healer. pve wise I'd call priest not sufficient enough and recommend summy or druid healer. Druid has more heal power output and aoe healing but summy has the legendary Dark Veil that can beat druid in certain aspects of the game.
can I eventually just switch my toon to another class through reincarnation system to keep my mounts and costumes or am I remembering that wrong?
Yes you can use reincs to play different classes BUT your gear is seperate per char(reinc) so you will have to re-gear them or be weak when swapping from mains to others, even tho gearing is fairly easy now.
You can also swap classes with core morphers and remain on the same character but that's going to take a big chunk out of your wallet.
On p2p server the core morphers are weekly from the AH for only gold, starting from 5k and gone up to however much people feel like bidding.