Goggins is arguably better in The Shield than in Justified, but the role is much, much darker. Caveat emptor, The Shield is brilliant but it isn't for everyone. Be prepared to hate just about everyone in that show, they don't sugar-coat anything or pander. I really need to revisit this show, but for reasons that will be obvious after you've seen it, it isn't a world I want to spend a lot of time in.
My Timothy Olyphant theory: He was so good as Seth Bullock in Deadwood, playing an obvious badass who never actually did anything badass, they adapted Elmore Leonard's novels to create Justified specifically with him in mind so we could see him menace AND kick ass.
If you're looking to see Olyphant in a different light, check this out. It's much better and more clever than the trailer suggests.