Okay let me tell you the low down on hunter builds for PVE strictly talking about solo build here.
I have tried marskmen build which is by far the most popular but from my past experiences with my hunter I started as best spec cause I was a dwarf and it wasnt popular this is before the big skill tree change. Now I noticed my pet cant hold agro from me I do have a blue rifle and crit good amount sure the numbers are nice but sometimes you get ganked by some gay spider walking by ect..
With markman shipbuild its hard to survive a fight with a creature 3-4 lvls above you if another one adds. But with beast build its pretty easy target the add tell beast to attack it do that until it has agro switch it back to orginal target start firing away. Also at early level hunter its okay to melee heck even 30+ you still melee sometimes your pet should hold agro even with a blue 2 handed weapon on. The most creatures I survived at once was about 4 wolf when I was lvling around darkshores that was all at once than shortly after I had 2 more attack thankfully not all at once but my dear fullfy nearly was dead take off taunt and use distracting shot and tank if you have life or potions if not use wing clip followed by dazing shot run short distance away channel as much mend as you can to your pet have him taunt again and keep tring to heal him.

Also your pet w/o beast skilltree has harder time hold agro due to its lower dps you wont miss markmenship trust me this is an almost no down time lvling build Marksmen is great for PVP but waste alot of mana in PVE when you can just weaken it up and run in with big axe to finish it ^^.