Monodominants are different. They believe that it is the right of mankind to rule the galaxy in the Emperor's name, and they plan to achieve this by destroying forever the Emperor’s enemies. Xanthites believe that Chaos cannot be defeated, but its power can be harnessed in service of mankind.
That leaves plenty of areas in between. So you could have a Monodominant who believes that is the right of mankind to rule the galaxy in the Emperor's name and the best way to do this is by harnessing Chaos and using it to destroy mankind's enemies including, in the end, the powers of Chaos themselves. Or you could have a Xanthite who believes that the power of Chaos can be harnessed in service of mankind - and his plan for that power is to use it to wipe out the enemies of humanity (except Chaos itself as it is merely a reflection of humanity).
Monodomination, in my eyes, is more than simply being intolerant of heresy in all it's guises - it's about believing that the way to ensure that mankind achieves it's destiny is by wiping out everyone else. All* Inquisitors are intolerant of heresy, but not all agree on what constitutes heresy, and some see themselves as being above committing heresy. Likewise all* Inquisitors seek to destroy the enemies of the Imperium, and thus share some beliefs with the Monodominants, but that in no way means that their beliefs are sub-sets of the Monodominant beliefs.
* When I say 'all', I of course accept that there are exceptions - but rooting out heresy and defending the Imperium is an Inquisitor's job after all.
EDIT: Another thing I'd suggest is that the tenets that Draco proposed be the work of Jeriminus rather than Goldo. Goldo concluded that that the only way the Emperor’s loyal servants would survive in the galaxy was if everything else was destroyed. The tenets seem to fit more with Jeriminus taking Goldo's conclusion, turning it into a 'mission statement' for Monodomination - they'd be one of the things that helped bring Monodominance to prominence within the Inquisition.