I think the Horsemen have won the challenges fair and square, including the veto challenge from this last episode. All the challenges have been very balanced in fair, in my opinion.
1ST HOH - Jase and Scott win on treadmill. But I'm convinced that Scott outlasts Karen because Jase had done better on the quiz section which kept Scott's treadmill set slower for a longer period of time. 4H won b/c of brains. All things being equal, Karen would have outlasted him.
1st VETO - Scott wins, right? They throw hula hoops. They weigh, what a pound or so? My 80 year old grandma could throw one. This is more a skill than anything else, and really, who practices throwing hula hoops? Everyone was on equal footing. And Jennifer aka Nicomas didn't even try to aim for the flamigos. She tanked it.
2nd HOH - Marvin wins for answering questions in the majority. Again, no physical skill needed here. It was brains. The women could have (and should have) won this one.
2nd VETO - Jase wins. Ok, there is some physical strength needed, but that's not the main component. Jase was smarter for rolling his rope around his arm. Lori was neck and neck with him, which shows that Jase's superior size and strength wasn't really the edge. His technique (and maybe working with Drew, which is strategy) won it.