priest and druid have something shamans dont have, that's reflection and meditation. Gives around 15% mana regen in combat, it gets better with more spirit
that's why we need mp5
i would say stamina int healing and mp5. spirit is complelety useless in raids because you don't have any time to regen your mana abit
get as much mp5 and healing as possible
this dude is amazing http://www.classicwow.com/forum/topic/15129-the-egregious-guide-to-resto-shaman/ this guide will show what you need
i don't know anything about pvp gear, but resto/ele is the best choice, tho you need some spell power instead of healing power to increase your dps and healing at the sametime