noob question on Expertise/Improved Expertise

[ven]

In the General Build Guidelines (that I saw in the huge .PDF file, and the thread stickied here), under Melee builds, it lists Expertise and Improved Expertise as suggested feats for HG.
I am curious, why?
Is it primarily for WMs, or is it Melee chars in general? Still new to this and I don't understand why Expertise/Improved Expertise is good, unless you are going to be a WM.
Would appreciate any explanation.

[khaine]

I don't have a melee build, but I would it is because later on in life you are mostly not a damage dealer, you are a brick to hold up the enemy while mages fire of devastating spells of epic proportion

[FunkySwerve]

They're good because they provide an extra 5 or 10 ac that stacks with anything - which comes in very handy in high-level areas. Definitely not just for WMs.

Funky