By any code I'm aware of, what you have there is a properly vented lavatory and an unvented toilet and tub. A wet vent is supposed to be 2" minimum, and to be correct the tub drain would have to wye off the toilet drain (3"x 2" wye rolled above the centerline of the 3" run), and the lav drain/wet vent would have to wye off the tub drain (2" wye rolled above the centerline of the horizontal tub drain).
I think a 2" vent stack serving a laundry in the location you've decribed wouldn't hurt anything. That would make the 2" stack the (sort of/default) faux wet vent for the toilet and tub. Some jurisdictions (like mine) do not allow a washing machine drain to be used as a wet vent; some do.
I think a 2" vent stack serving a laundry in the location you've decribed wouldn't hurt anything. That would make the 2" stack the (sort of/default) faux wet vent for the toilet and tub. Some jurisdictions (like mine) do not allow a washing machine drain to be used as a wet vent; some do.
