It's a common mistake, but an error nonetheless. Again, Rev. 6:10 says, "How long, O Lord, holy and true, dost thou not judge and avenge our blood on them that dwell on the earth?" They are told to wait, not that the judgment has begun. Ergo, there is no judgment of God through the fifth seal at least.
Not all the scholars in the world stack up against a single word of Scripture.
As for the fifth seal, this does not appear to be the age of grace.
This is precisely why I am not a Dispensationalist. Salvation has always been by grace received in faith rather than by keeping the Torah (Rom. 4), and even to the present age, the Messiah said,
"Think not that I am come to destroy the Torah, or the Prophets: I am not come to destroy, but to fulfil. For verily I say unto you, till heaven and earth pass, one jot or one tittle shall in no wise pass from the Torah, till all be fulfilled. Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven."Your argument is a common one, but not one universally held, nor an insoluable one in the face of Scripture:
--Matt. 5:17-19
Barnhouse proposes that the cry of these martyrs proves that the Church has been previously Raptured. “Can it be considered for one instant that these souls who, of course, have left their old nature far behind, can be crying out for vengeance to God in Heaven in a time that is still in the age of grace? This is impossible.”[1] On the contrary, as Seiss writes, “Such a cry would be out of season, except in this place. But it is the time of judgment. The judgment throne is set. The judgment proceedings have commenced.”[2] These saints cry out for God’s justice for His name’s sake, even as Moses cried out for His mercy for Israel for the same reason.[3]Nor is it out of place to do so. “These saints are following the teaching of Sha’ul in Romans 12:19, ‘Do not take revenge, my friends, but leave room for God’s wrath, for it is written, “’It is mine to avenge, I will repay,’ says the Lord.”’”[4] Indeed, did not Sha’ul himself say with confidence after Alexander the coppersmith turned on him, “The Lord repay him according to his works”?[5] There is nothing wrong with praying that justice and righteousness be done, as we can see by simply perusing a few of the Psalms. Nor is there any contradiction between praying for God to vindicate His righteousness at the same time that we pray for our enemies to find His mercy—and certainly not in a time when those enemies will put themselves outside of His mercy altogether, as we will see in chapters 13-14.
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References:
[1] Barnhouse, Donald Grey, Revelation: An Expositional Commentary (Zondervan, 1971), p. 134
[2] Seiss, Joseph A., The Apocalypse: An Exposition of the Book of Revelation, (Kregel, 1987 reprint), p. 147
[3] Dt. 9:28
[4] Johnson, Alan F., Revelation (The Expositor’s Bible Commentary, Vol. 12, Gaebelein, Frank E., ed.) (Zondervan, 1981), p. 475
[5] 2 Ti. 4:14