"When claims involve a conflict or tension that stops short of actual logical conflict--of strict inconsistency--this is generally indicative of irony rather than paradox. It is ironic (rather than paradoxical) that the competent general must both protect his soldiery and endanger them by use, and that he cannot do the one without forgoing the other. It is ironic (rather than paradoxical) that the individual soldier cannot pursue glory without putting his life at risk" (Nicholas Rescher, Paradoxes, 7).
The tendency whenever we find someone carrying on some way of life with a tension in it is to suppose that it mustn't be a strict contradiction--else it would be impossible. But I'm not sure. The Knight of Faith might well become alienated, neither belonging in the world in which her belief is true nor in the world in which it is false. And alienation and irony, as we all know, go together. Contradictory beliefs tear one apart as much as purposes that slightly undermine each other. Rather, they do so insofar as one is given to maintaining a consistent set of beliefs.
It would not be quite right to call the Knight of Faith's position 'ironic'; it's tragic, perhaps impossible, but not ironic. Her attitude, on the other hand, might well be one of irony. There's no other way to go about it (that I could imagine, anyway): "Yes, this is what I'm doing--sacrificing my only son--; because I must, though I don't know why; here I am, doing it...." There is a difference between this sort of detachment, wide-eyed and believing and disbelieving, and the mood of wry, knowing irony.
The difference between the general in Rescher's example and the Knight of Faith can be made larger or smaller: whether the general's position literally involves a contradiction will depend on how we write it, and perhaps on how it figures in the intentions and beliefs of the person who holds it. "I've got to keep you safe so I can endanger you" is probably the belief and/or intention of someone who, if he or she falls into one of these two categories, is wry or ironic. "I must keep you safe in order to endanger you" is likewise. There will be detachment approaching the Knight of Faith's to the degree that wanting to do things that endanger one's troops and wanting to protect them are motives one has separately, and not as part of the compound that is the job description.
"I must endanger you in order to keep you safe" is closer to the Knight of Faith: an uncomprehending detachment in the face of a world--of a path through the world--that does not make sense. Here what's paradoxical is the causal relation between these two things. Though of course it may turn out that the causal relation was straightforward--just dependent on factors beyond the comprehension of the Knight. There are certainly cases in which one must go away from one's goal in order to reach it ("sometimes you have to go a great distance out of your way in order to come back a short distance correctly"). Though it tears one apart no less in the meantime. As with all contradictions.