What is the standard of review in the context of the "patently unreasonable" test?

The standard of review in much of what has been considered herein is the “patently unreasonable” test. While, as my comments above indicate, I do not agree with the arbitrator’s decisions respecting the articles in question and indeed think the decisions to be in error, I would be uneasy to characterize the arbitrator’s conclusions as “patently unreasonable” in the light of comments such as those of Iacobucci J. in Canada v. Southam (1997) 1997 CanLII 385 (SCC), 1 S.C.R. 748 where he says at p. 777: The difference ... lies in the immediacy or obviousness of the defect. If the defect is apparent on the face of the tribunal’s reasons then the tribunal’s decision is patently unreasonable but if it takes some significant searching or testing to find the defect then the decision is unreasonable but not patently unreasonable.