I think you guys just reply for the post counts at least 95% of the time.
Best horde race ?
Each race has its own advantages depending on your play style each can be great , for me as i am trying all 4 horde races that can be a hunter i see very little difference at levels 21 to 30 .
Want to be good at pvp ? Well i guess everyone will have their choice of race , My guess it would be bloodelf against casters or tauren for their stomp to slow the enemy.
as for talent builds there are so many different views on them and slight differences i would read the threads at the top of the page , as with all talent trees there are some talents that are not so great , read up on each to see what others have used or not used , most trees give you two or three choices at each five point level , pick the best ones you can , things that help do more damage or make pet stay alive longer and do more damage are the ones to go for .
Another thing with pvp depending on your level can be a trade to help you , Engineering for example gives you explosives and as you get higher robots and exploding sheep all work well as a damage bonus , There are so many different choices you can make and most can work ok .
The main thing to remember is all the races are good , All three talent trees can work well , but for me beastmaster rules while trying to level , i did try marksman/survival at lowish level once but soon changed back to BM...