Since it was requested I put this information in the Hawkeye sub forums, here goes.
In order to brutally strike all the time we need to meet a few conditions.
First, only use arrow powers. For some reason Elusive Arrow, Explosive Arrow and trick arrowheads are not being treated as arrow powers. So these must be removed from your build. This includes Three Arrow Burst and Overwhelming Force as they shoot Explosive Arrow.
Next, you need 100% brutal strike chance. At the moment, this is only achievable through arrow powers(hence this being in Hawkeye's sub forums). You need Clint's Custom Quiver omega set up to rank 3 for the 50% bonus chance. The other 50% can be obtained through a mixture of gear and infinity.
If you want to only use gear, it takes 6500 brutal strike rating to achieve 50% chance. You can have up to 5% brutal strike chance from infinity as well, reducing your needs to 5200 brutal strike rating.
Then you use at least 1 piece of the omega set Gamora's Garments. This will give you 100% critical hit chance after building up stacks. These stacks only go away from 4 different ways:
1. Getting a critical hit(not a brutal strike)
3. Logging off of the game
4. Switching characters
The stacks are NOT removed from switching maps, so unless you die or use a damage source that isn't an arrow power your stacks won't go away until you stop playing as Hawkeye.
Now I will say the build I personally use starting with talents
As for powers I am currently using
1. Acrobatic Roll(dash)
2. StarkTeck Claymore Turret(sig)
3. Serrated Arrow(main basic and DPS)
4. Speed Loader Volley
5. Shrieking Arrow
6. Nerve Gas Arrow
7. StarkTeck Medical Arrow(optional)
8. Wave of Arrows(optional)
You could use Electric Arrow or Freeze Arrow instead of Wave of Arrows. You could also use the Thread the Needle talent and use Rocket Arrow or Boomerang Arrow. However, Rocket Arrow currently has a bug and isn't receiving a 100% crit chance. So I'd rather use a trick arrow myself.
You can also use Flash Bomb instead of the medical arrow, or even neither and go all damaging powers.
Never use trick arrows and rocket arrow/boomerang arrow in the same build, as trick arrowheads don't receive the 50% bonus brute strike chance and will remove your gamora stacks.