Holocaust revisionism is something I have heard mentioned a few times and my knee-jerk reaction is to see it as Holocaust Denial. However, it was described to me as an attempt to find the truth of the Holocaust and to stop it being taboo to find things or research against accepted history.
This was described to me by someone very interested in WWII and the Holocaust and usually of a sound moral compass, which led me to give them the benefit of the doubt and seek your help.
TLDR: YES
Mainstream Historians of the Holocaust would recognize them as deniers. Groups like the IHR or individuals like David Irving are treated by the academic community as deniers, even though they would not espouse the label themselves.
I would read Deborah Lipstadt's Denying the Holocaust for a pretty damning case against Irving and other so-called "revisionists". Lipstadt, who is on the Academic Committee at the United States Holocaust Memorial Museum - the center of Holocaust research in North America - was actually sued by Irving for libel. She won hands down, with major names in the field of Holocaust history siding with Lipstadt against Irving, including Chris Browning (UNC Chapel Hill), Peter Longerich (University of London), Richard Evans (Cambridge), and Robert Jan van Pelt (University of Toronto).
EDIT: to be clear, those scholars didn't just side with Lipstadt - they testified at the trial on her behalf.
As long as we are careful not to include work by people like Timothy Snyder as a revisionist, I think it's okay to call them deniers.