There has been Revisionism of the early Church father's writings by some of today's Pre-trib scholars who have been caught falsifying. That's obviously where you got your info about Irenaeus who believed in a post-tribulation coming of our Lord Jesus and gathering of His Church...
Irenaeus:
"But he indicates the number of the name now, that when this man comes we may avoid him, being aware who he is: the name, however, is suppressed, because it is not worthy of being proclaimed by the Holy Spirit. For if it had been declared by Him, he (Antichrist) might perhaps continue for a long period. But now as "he was, and is not, and shall ascend out of the abyss, and goes into perdition,"(1) as one who has no existence; so neither has his name been declared, for the name of that which does not exist is not proclaimed. But when this Antichrist shall have devastated all things in this world, he will reign for three years and six months, and sit in the temple at Jerusalem; and then the Lord will come from heaven in the clouds, in the glory of the Father, sending this man and those who follow him into the lake of fire; but bringing in for the righteous the times of the kingdom, that is, the rest, the hallowed seventh day; and restoring to Abraham the promised inheritance, in which kingdom the Lord declared, that "many coming from the east and from the west should sit down with Abraham, Isaac, and Jacob." (Irenaeus: Against Heresies, book V.30.4)
In a still clearer light has John, in the Apocalypse, indicated to the Lord's disciples what shall happen in the last times, and concerning the ten kings who shall then arise, among whom the empire which now rules [the earth] shall be partitioned. He teaches us what the ten horns shall be which were seen by Daniel, telling us that thus it had been said to him: "And the ten horns which thou sawest are ten kings, who have received no kingdom as yet, but shall receive power as if kings one hour with the beast. These have one mind, and give their strength and power to the beast. These shall make war with the Lamb, and the Lamb shall overcome them, because He is the Lord of lords and the King of kings."(11) It is manifest, therefore, that of these [potentates], he who is to come shall slay three, and subject the remainder to his power, and that he shall be himself the eighth among them. And they shall lay Babylon waste, and burn her with fire, and shall give their kingdom to the beast, and put the Church to flight. After that they shall be destroyed by the coming of our Lord. (Irenaeus: Against Heresies, book V.26.1)
That idea he says of the Antichrist putting the Church to flight is not about a pre-trib rapture. It's about Christ's command for those in Judea to flee to the mountains when they see the "abomination of desolation" placed in Jerusalem by the Antichrist.