You should roll 25 male tauren shamans, warstomp is very powerful (you can setup macros in WoW so it chains them, basically melee would be CC'd for a while). Troll racials are terrible. Orc racials are good, but mainly best for PVP warriors (stacking stun resist) and hunters. Once you get a male tauren geared out, they look incredibly badass, plus they are absolutely huge which is an advantage in multiboxing for both you and in PVP.

Blackrock is a good server, one of the top in PVE progression and its part of battlegroup9. Lots of alliance who do world PVP on it as well, in small groups, so they will be blown away by 25 man team.