You are correct o find most raven's Active tank fitted, you will also find a few passive/buffer fit.

The buffer fit i generally tend to see is 2 Large Shield Extenders IIs with 2 Invul Field IIs 100 MWD, however this fit also fits PVP better, as most active/specific resist tanks for mission is usually the norm. You could easily spider tank with a BS setup, i generally use 1 BS ie: Domi, and then 2 to 3 Tengus/or Drakes and have them orbit the BS to get their angular velocity up and always moving.

Most of the time everything is targeting the domi which is easy to dual rep perma tank 1200+ dps.