From the time of Christ to today millions into billions of Christians have been murdered, tortured, imprisoned, harassed etc.
Therefore the great tribulation is great because so lengthy (2000 years or so in duration), also because of the huge number of people who have suffered, and thirdly because of its degree of viciousness.
So yes, for some 2000 years there has been great tribulation. In the Sudan, other Arabic lands and some places in Southeast Asia it is continuing this very second. There is a scripture indicating that it began with Christ leaving the earth, none saying after 1914 or the like.
As to JWs being under tribulation, no, it's more like the Watchtower Society heads who keep pro-pedophile policies going who are under tribulation and rightly so by the Courts, Police, those of us upset with the wrongs and injustices they perpetrate.