I too, thought universalism was a heresy until I spoke to my priest (who I trust), and was pointed to what the scriptures and the saints have to say about it.
I must strongly caution everyone that the blog you linked is not Orthodox. In his about section he mentions he isn't a practicing priest for reasons he doesn't want to go into (first red flag).
His wife is seriously ill and he is retired from the ministry as a result.
recommend reading Unquenchable Fire: The Traditional Orthodox Teaching About Hell by Fr. Lawrence Farley
I'd suggest, as a better resource,
On the Soul and the Resurrection by St. Gregory of Nyssa. As well the epistles of St. Paul,
On the Incarnation by St. Athanasius, and the hymnography of our Church (last Sunday's first troparion, among others).
to understand why. Apokatastasis (Universalism) is directly refuted in the Bible, particularly Matthew Chapter 25, which ends with verse 46: "And these shall go away into everlasting punishment: but the righteous into life eternal." It's everlasting, not just a long time.
Translated literally, Matthew 25:46 states: "And these shall go away to punishment age-during, but the righteous to life age-during." (Young's Literal Translation). Translating αιων one way in when it fits our theological bias, and another way when it doesn't, -for example, differently in Matthew 13:49 than in 25:46- seems to me to be a bad habit.
In addition, a more literal translation leaves in a position where St. Paul's epistles no longer have to be explained away (1 Tim. 4:10, Romans 9-11, etc.).
If Hell were only temporary, that would mean the Church, sacraments, and following Christ is optional if you ultimately want to get to Heaven.
Father John Whiteford, who I trust, wrote this rebuttal of Fr Aidan Kimel's stance on Universalism.
I find such a cavalier attitude towards hell difficult to understand. If you love God, which is difficult not to do once you realize the gift that he's given mankind, then you'll want to help others escape the fires of hell.
Also in his blog he lists far more "western" Christian authors and books, including many heretics, as influences on him than "eastern."
It should not come as a suprise that a priest who found his way from the Episcopal Church to the Roman Church all the way into the fullness of Orthodoxy would be pointed in our direction by many others. I myself would not have become a Christian, or Orthodox, without the writings of certain Roman Catholics and Protestants. Martin Luther himself said that the truth lies with the Greeks; it should be no surprise that people have found Orthodoxy as a result of him.