The best way to solve the problem of adding too much rosemary to cooking is to remove it as soon as you realize your mistake. Or you can dilute it with adding more of other flavors. Alternatively you can dilute by doubling your portions, or adding tomatoes or even dairy products like sour cream.
Tarragon has a stronger flavor profile to dill and will stand up to the heat of cooking, whereas dill will wilt if used fresh in stews or soups. Dill tastes like a gentle citrus grassy flavor with hints of anise, tarragon is strong and astringent anise licorice flavor with an earthiness.