I don't like making the same mistake twice, but I hate doing theory-craft math on my own. I can't trust the Armory to know everything. (Remember, the Armory & similar databases look at gear as a whole for your class.) The trick is to find a good calculator to help and to invest the time to plug in gear and tweak numbers.
I've been using Cheeky's Spreadsheet on Elitist Jerks for a hunter calculator. To use the spreadsheet, you must enable macros. In other words, use at your own risk. The spreadsheet itself can take time to get used to. The good news is that you will learn about your gear no matter how much work you put into it. The big thing to understand is that the numbers are still theoretical. It's up to you to maximize your potential.
But Beroth, that sounds like a lot of work. Why can't I just trust the Armory and read the forums? If you aren't serious about endgame or don't mind the occasional downgrade, then by all means, do so. But let me show you what I'm talking about.
I plugged my gear into the spreadsheet and got approximately 900 dps unbuffed (including Pet.) That translates into roughly 1050 dps w/ raid buffs & food. (Again, these numbers only hold up in theoretical situations. My actual numbers will vary.)
Once you've gotten all your gear organized, you can play with gem options & pets to find your best combination. Simply changing a few gems can add 10-20 dps. Swapping pets can make a huge difference. Sometimes you may want one pet, but your gear/build dictates than another is better. The first time I used the spreadsheet, I swapped pets, changed my food & spent nearly 400 gold on gems to add over 50 dps. I have the raid stats to back it up!
Putting the Spreadsheet to the test
You may have read that Beastmasters prefer the Wolfslayer or the Barrel-Blade guns over all other ranged weapons. But have you ever tested it? I have.
I currently use the Wolfslayer Sniper Rifle. The armory ranks it as 9th with an item level of 115. Whole threads have been devoted to the Wolfslayer being the 2nd best Beast Master weapon in the game. Let's take a moment to compare it to the highest ranked weapon in the Armory and see what happens.
Weapon - Hunter DPS - Total DPS - Buff'ed DPS (Aspect of Viper)
Wolfslayer Sniper Rifle - 655.52 - 914.11 - 1084.06
Serpent Spine Longbow - 647.73 - 903.85 - 1068.91
Let's now add the 13th ranked weapon
Barrel-Blade Longrifle - 668.37 - 926.81 - 1098.72
What gives? The Beast Master talent, Serpent Swiftness makes the statistically worse gun becomes better because of it's faster base speed. This is the prime example of why you can't just trust the Armory. You've got to take time to understand your gear, your talents and how they all work together. A good spreadsheet will help.
PS. My theoretical DPS w/ Aspect of the Hawk is over 1200! If only I could sustain that w/out running out of mana! Imagine if I had my own dedicated Shadow Priest! My numbers also don't include short-term buffs such as rapid fire or effects like shaman heroism.