For spellhance pickin’s are slim after Tier 7 content. In T7 you have Wraith Strike which is a respectable 2.6 speed. After that you have:
- Lockjaw - Rotface 10m - ICC - 2.2
- Valius - LC 10m - ICC - 2.2
In between you are stuck with 1.8 speed main hands. You’ll still see benefits from having a slow offhand as to increase the Maelstrom proc chance for lava lash and offhand hit of stormstrike.
The flurry behavior isn’t as big of a deal in wrath as your uptime on Elemental Devastation will be much higher with the number of spells being cast. The +9 melee crit this provides makes it much easier to maintain near 100% uptime on flurry even if your weapon speeds aren’t matched and your swings unsynched.
Also note that once you get enough melee haste to drop your GCD down to .75 seconds (not including flurry as it doesn’t count towards GCD reduction) overcapping on maelstrom charges is much less frequent if you have good reaction time. You’ll likely only have one swing after capping before your GCD is available to LB.