1) The fact that the Black Court got essentially broken as a geopolitical power by a lot of motivated mortals and lesser supernaturals who exploited exposed weaknesses does not mean they did not use to be a major power.[X] The Skinwalker and the connection to framing Harry and the White Court connection via the attempt on Sarah Greene's life
If this was true, White Court could never have become a major world player. An angered party of wizards during Rome era would have wiped them out in a busy afternoon.
Thats a little like saying that if a surprise attack can knock over the White House, then the US is not a world power.
Or, alternatively, see Shagnasty rolling the Raith Estate solo at literally minutes notice in Turn Coat.
And not just the Raith Estate and its defenders, but Dresden and Luccio as well, who were respectively the Warden regional commander for the eastern US, and the Warden Captain-General.
2)Not all power is hard power.
3)Law-abiding Wizards are at particular disadvantage when dealing with Whites because of their requirements to try to avoid killing mortals. A Whampire behind a meat shield of mortal goons is not something the White Council is especially keen to engage if they can avoid it.
4) Estimated world population at the time of Rome's maximum power circa 200 AD was between 200 and 250 million.
Assuming 1 in 100k were wizards, thats a maximum of 2500 wizards worldwide.
You can do the math yourself.