You may call as a subordinating conjunction, as is the case in traditional grammar, or a preposition, as is the case in CGEL. It doesn't really matter what you call it.
The subject of the as clause is not such issues but the entire superordinate clause. What was seen was not the issues but their arising. You might paraphrase
That such issues can arise was seen in [&c] OR
In [&c] it was seen that such issues can arise.
An explicit subject within the subordinate clause is not required; when an explicit subject is absent the construction is understood to take a preceding clause or constituent as its subject. The same phenomenon may be observed with other constructions:
1.Bill wants Susan to go to the party.
2.Bill wants to go to the party.
In 2, Bill is the subject of both want and go, so we do not need to say Bill wants Bill to go to the party.
The verb is singular because its subject is singular.
In the 'p.43' quotation, likewise, the subject is the preceding clause his experience ... review. What was made evident was the inability of Mr. Clarke's experience to save the legal system.
These are comparative constructions (like as...as, same...as, such...as) of a special kind: the initial as or same or such is omitted because what is being compared is things which are equal. The phenomenon expressed in the head clause is 'like' or the same as what is seen or evident (or, in my 1., the case) in the subordinate clause.