Good question.   It is true that the evidence outside of Christian sources for the persecution under Domitian is relatively small.   It is also true that if it were nor for a single reference by Tacitus, we would have no reference at all to the persecution of the Christians in Rome by Nero, other than Christian references, of course.   There is an untold number of events–including rather major events–which occurred during the Roman empire for which we have no surviving record.   Many scholars have an extremely, dare I say irrationally bias against any historical events recorded in the Bible or in Christian sources.  They will accept the slightest evidence from a non-Chrisitan as proof positive that an event happened, but no matter how many Christian sources there are for the persecution under Domitian, they are rejected as irrelevant unless they are also corroborated by a secular source.   The problem there is that the most likely group, by far, to report a persecution of the Christians, particularly in the first one hundred years of the church when it was still relatively small, is obviously the Christians.   Both Tacitus and Seutonius say relatively little about the Christians, including the persecutions against them, because they were a relatively insignificant group in the first decade of the second century.  Yet, both of them definitely report that they were a persecuted and reviled group, which is fully in concord with the Christian description of the persecutions under Domitian.  There are numerous Christian sources for the persecution under Domitian, which includes the book of Revelation, of course, which has John on Patmos because of this persecution.  Eusebius mentions it, saying it broke out in the fifteenth year of Domitian (AD 96), as do many others.   Do these scholars think that all are lying about this?   This bias against accepting Christian records of their own persecutions is not a sign of good scholarship, but of extremely unbalanced treatment of the data.

Can we count on the absolute truth of everything Eusebius ever reported?  No.  He is known for reporting things which may be heresay.  However, both the amount of detail in his account and the number of reliable historical references, both in the New Testament and in early Christian writings to the systematic persecutions under Domitian make it a very secure conclusion that these persecutions did indeed happen.   In fact, if you read Pliny the Younger, he is reporting back to Trajan about his arrest of the Christians.  He appears to be working under a general prohibition against those who took the name Christian which predated his term of office in Asia Minor.   Almost certainly he was working under the order which was put out by Domitian, as reported by Eusebius.

So, you are fully justified in concluding that there was a widespread if not general persecution of the church under Domitian in the last decade of the first century AD.

John Oakes, PhD