Looking at your gear, you *should* be more than fine. Unbuffed you're running between 50 and 55% avoidance, and you have a fairly decent health pool. You say you're keeping Thunderclap and Demoralizing Shout active, so you're doing your part (Although you may consider investing in Indestructible Potions to help further cut down on melee)
For your expertise question; it isn't really "needed" but it certainly is wanted. It is primarily a threat stat, but keep in mind that if a boss parries you it will haste their next attack. This isn't always an issue, but it can result in a death from spike damage. It's strongly advised to at least have around 30 expertise. You don't need the hardcap per se, just a fair bit more than you have.
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