Frost DK meets many of your requirements, except high mobility, but only in the TWW beta as of right now; in retail it is rather “meh”.
Tuning passes may change this, but right now in the beta Frost DK is an in extremely nice spot, arguably one of the top-3 melee dps specs, if not the best. The rotation is comparatively simple with few buttons, survivability is solid, tons of damage with short CDs that are up for most packs in M+. Bonus: if you ever wanted to be one of the best tank classes for low to medium-high keys, you can respec to Blood (and use the same weapon).
But all of this can still change.