Discretion when selecting your gear is important. There are a certain set of shoulders that while i245 are not very well suited for a warrior. I take the honorbound helm over the tier one because of the expertise, same with feverish dedication legs, and tower monstrosity BP. I'm rocking 45 expertise plus in my standard gear, and maintaining about 22 hit. (only piece with hit is the throwing weapon).
Remember that when it comes to warrior tanking, 90% of our standard rotation is avoidable. This means that expertise becomes extremely valuable.
Expertise and hit provide a very similar result, but go about it in different ways. Both "Increase the chance an attack will land against your target". While hit effects every skill, expertise only effects those which are avoidable. Obviously before the expertise soft cap expertise is better, but what about after the soft cap and before the hard cap? Expertise is still better. As long as your attack is avoidable they both increase the chance your attack will land by the same amount. However, expertise still reduces the chance of parry gibs, while hit does not.
Hit is obviously critical for those abilities which are not avoidable. Stuff like taunt, demo shout, thunder clap, shockwave. All of these (among others) are only effected by hit, not expertise. Many have work arounds like the taunt glyph, or demo shout being applied by your ret pally and TC applied by your DK etc.
The trick is understanding when hit is important... can't miss an interrupt? Get hit. Need to push insane TPS on Hodir? Expertise.
Regardless, gear is not nearly as important for generating threat as rotation priority and spamming heroic strike. Heroic strike is a good 38% of my threat on a good night... that's insane. Many people like the heroic strike on the mouse wheel, I prefer it on my "back" button on my mouse. Either way, find ways to make spamming it easier, and you'll do it more.
Outside of that there are rotations that will allow you to maximize your sword and board procs in order to push out more shield slams. Devastate glyph also makes a noticeable difference, but these final two points are only meant to refine and maximize your threat as needed.