In addition to airfield base defense as prevoiusly mentioned, I like to take the Hurri I or IIC out to a friendly VB that's being attacked. Generally the enemys are lower and somewhat spread out giving you a little breathing room between fights and a chance to break away for home or simply land when needed.
If things slow down I head toward the base they were upping from and usually draw them back out.
While it's still a defensive role it feels a little more offensive when you actually have to fly somewhere.
BTW, I really have fun in the Mk I. The 8 .303's are pretty stout in close and the engine shut-off under negative G's doesn't seem to really bother me because it will automatically re-fire once the G loading changes again.