My Root Guru and His wife always used to argue over the necessity of Protector prayers and offerings. He was primarily a Dzogchenpa Who took the POV that, as long as He was in the state or otherwise practicing the Dharma properly, the Protectors would automatically do everything They are entrusted to do. His wife, more a Mahayoga specialist, would always want to do long Protector prayers at drupchods and other such opportunities. Her POV was two-fold: 1) To confess and repair any broken samaya so as not to experience the chastisement of the Protectors, and 2) to request the Protectors to avert disasters and fix negative things in this world of apparent exitence. She would say, "I don't have the power to make this or that change in the world, but the Protectors do." (BTW, She is an extremely powerful yogini for whom CNNR once wrote a shabten acknowledging that fact.) Sometimes Their arguments occurred right during the ceremonies. My Teacher would often nudge His wife to wrap up it with the Protector prayers -- enough already. She would then scold Him and keep on banging the drum and saying more and more prayers with visibly intense concentration and conviction. Eventually He would put down His dorje and bell and simply sit in meditation until after the prayers were over. I'm not telling this story out of a desire to criticize or gossip about either my Teacher or His wife. To me this story is more about valid differences of opinion about practice. Each practitioner has his or her own beliefs, style, and habits and is at their own stage.
As an example of the second kind of activity alluded to above by my Teacher's wife, for a year, Lama Dawa was having premonitions/dreams of a major earthquake in March. After a medium quake in Mexico a couple of hundred miles from where He was teaching but where He felt the tremor, He put out the word to His sangha to do a certain Guru Rinpoche practice invoking specific Protectors and Lords of the Earth to stabilize the elements of earth and water and prevent earthquakes. AFAIK, there was no major earthquake with catastrophic loss of life during March. For me, this was an example of the application of skillful means as the occasion demanded prompted by great compassion for sentient beings. (As a humorous aside, I had to go to Berkeley, CA during March to attend a teaching with another Lama. Berkeley/SF sitting on the San Andreas fault as they do, you can bet I put in over-time on this practice while I was there.)
Personally, when I do Protector practices (which I do most afternoons), I do so primarily for this second purpose of working for the sake of suffering sentient beings, invoking Them to do what I don't have the power to do.
Pema Chophel པདྨ་ཆོས་འཕེལ