I consider the VP exposing a CIA agent and putting her life at risk because he was pissy about her husband's op-ed to be pretty damned serious. I also consider the overt politicization of the Justice Department by the president to be pretty damned awful. Those are real life abuses of executive power to punish political enemies, not some low-level IRS people acting badly and the IRS coming forward with this information voluntarily. They were way, way worse.
I also limited myself to post-Watergate since you started there, but there are plenty of other truly awful abuses of power in American history going back to its earliest days that are way, way worse than this IRS thing.
Iran-Contra was one of the most despicable scandals in American history. Sitting president consciously violates the law, negotiates with and sells weapons to Islamic terrorists, funds nun-raping terrorists in Latin America, and Congress lets him off scot-free, and then America's gnat-size memory allows a PR campaign to turn one of our worst presidents into today's St Reagan mythology. The selective tax-exempt status approval decisions of some IRS employees is a laughable, pale little comparison.