Saddest,
Twice now you've mentioned following manufacturer's SOPs as being the safest policy. Having written or contributed on a number of AFMs, SOPs, FCTMs, QRHs and tinkering a bit with MELs for 3 major manufacturer's and for 1 large legacy carrier on at least 4 different types (Douglas Beoing, Airbus and Bombardier) I would be very careful with offering such advice.
The truth is that they're often full of errors and despite all the checks and balances some doozies do actually end up in the lap of crews. Believe me - absolutely nothing out there from the manufacturer's is gospel. It depends on the manufacturer but generally the AFM and the FCTM are probably the most reliable (error free) sources of operating info but neither, on their own, or in unison, can assemble a good SOP for practical real time scheduled commercial carrier operations. I think if you reviewed the opening comments in any AOM or FCOM SOP section you'll find that unlike in an AFM, the procedures given there are only recommended and further to that point I might add, in no way absolve the carrier from liabilty in the event of a accident.
That brings me back to your original question.
when does blind adherence to sops in itself ( if those sops are complicated ) become a serious flight safety hazard?
I think most would agree it's when airmanship is taken out of the equation.
Why some carriers go beyond that and micro manage them is beyond my own personal experience. Perhaps it's the variety of equipment, the mod status of each aircraft, operational neccessity, sometimes the inspectors/regulators are a little too by the book or anal, etc, - there's a myriad of reasons.
Perhaps also it's the nature of the crews and a function of their average training or experience related to the carrier itself . I could see where that might lead to a bit too much info in the SOPs and take some control out of the crews hands. In some cases it just might be well warranted though. The example that springs to mind is a retired colleague on a training contract on 744s for a bunch of folks who rode bicycles to work. Perhaps he was exaggerating bet their adventures (mis?) are well documented here on PPRUNE.
My last point is that SOPs are not static. They continuously evolve and strive to maintain a balance of too much info vs not enough for all of the crews. In a larger carrier the level of airmanship above a certain minimum ability varies quite a bit. Not everybody is ex USN or RAF or has 10 yrs on type in the left seat. Good for you if you're above the curve but you have to recognize that the newly transitioned F/O is just of his/her check ride and has limited line experience on type. You need for for him/her to maintain situational awareness and understand what you're doing. For that case an expanded SOP is one of his/her primary training tools.
In the end safety and avoiding liabilty is best achieved by balancing experience and knowledge against accepted practice and training. Airmanship and SOPs. Neither is foolproof and covers everything but in unison, getting the balance right goes a long way to making sure there aren't any headlines and board hearings.