StormerRyan on Oct 10, 2013 wrote:

Hey Kingslsle, I was confused on how talents work for other types of class like for example, my jack russel has a higher will, but boost damage on strong will like bonnie anne, she has high agile and boosts damage at the same time.

Why? Level 65 Stormy Ryan
Level 24 Dashing Ryan Kidd

Well Jack is a privateer and privateers use strength and will. His main boost will be strength and you can boost it higher as you level him.
Anne is a musketeer and her main strength is agility but you can, through training boost any stat you feel she needs.
When you use a boost like Juju it will give the boost that is needed based on whatever the weapon the fighter has. Since we cannot change our companion's weapons they will always get just what they need based on what their class generally needs. Privateer companions will boost strength and musketeers will boost agility. The will boost helps when they can also heal for you. The higher the will, the stronger the heal will get.
There are some good threads here on what training helps what class. Here is a recent one that covers some good points.