I think you may be focusing more on the 60% drop = bad WOM than the circumstances of this weekend though.
Spider-Man 3 had no competition in its second weekend. The #2 film made less than $10M. I'm sure if it was facing major competition, Spider-man 3 would have had a larger drop, but there was nothing else to see that weekend.
X-Men First Class had good WOM (reviews were high, IMDB user rating is 7.8, other sites show similar ratings) but still it dropped 56% in its second weekend. First Class was facing one film opening that appealed to a good portion of its demographic (Super 8, opening at $35M).
Man of Steel starts this weekend off at a disadvantage. Fathers day boosted the Sunday gross by at least $6M. The second Sunday drop will therefore be larger than it would have been if MoS opened on a regular weekend. Man of Steel also faces at least $100M in competition from the two major openers. WWZ directly plays to the same demographic. Monsters University has some overlap. At the very least, those films will steal some of the third and fourth screens MoS has been playing on in many of the larger venues.
A 60% drop with the inflated father's day's totals would be the same as a ~58% drop without them. That's only slightly higher than First Class' drop, and in the face of a lot more competition. I don't think that is a particularly outrageous scenario, especially in light of Wednesday's number.