刚看到这个，这是一个很好的问题！

1.The economic situation is as serious as was expected.

2.The economic situation is serious, as was expected.

先说第二句，这个比较简单。按照现在的语法认为是：as很像关系代词引导非限制性定语从句，as作主语，对应的是前面整个句子“The economic situation is serious”，这种语法结构很常见。我们熟悉的as you know也是这样，区别在于as you know的as是关系代词作宾语代替整个语句。

比如：

The world, as we know, is made up of small particles called atoms.

上面的第二句还可以改写为：

The economic situation is serious, as expected. 这里的as expected是一个习语，直接记住就可以。比如：

As expected ,  the Democrats won the majority of seats in Congress.

As expected ,  the party was a great success.

The parcel arrived the next day，as expected.

再说第一句，典型的as......as结构，你这样的写法的也有例句，很少：

Progress with the building of the bridge was not so good as was expected.（章振邦新编高级英语语法P674）

这个句子我认为不能算错，只是章振邦的解释我不同意：比较分句可以说省略了主语，也可以说是由as充当比较分句的主语。我对这个解释持保留意见。如果是说“省略了主语”，那没省略之前应该是as it was expected to be（as作表语，to be不要省略，那这就对了）。如果是说“由as充当比较分句的主语”，那as引导的限制性定语从句的先行词是什么，很怪的解释。

The firm isn't making out as well as was hoped.（朗文当代英语大辞典P1065）

There is not quite as much text as was expected.（The New Fowlers Modern English Usage2000第三版）

这里的as很像关系代词引导限制性定语从句，text是先行词，as作主语。所以这个句子没问题。

你提的这个第一句我认为不能说是错的，如同我举的章振邦的书上的那个例子一样，只是一般都不这么写，不太自然，一般写成以下的两种样子的比较多见：

a.The economic situation is as serious as it was expected to be.（as引导限制性定语从句，充当表语，没问题，先行词是serious）

b. The economic situation is as serious as expected. (as expected当习语用，就不用分析结构了)

举几个例子：

The figure of seventy-million pounds was twice as big as expected.

The damage wasn't quite as bad as expected.

It was as bad as expected.

The level of competence among hospital staff was not as high as expected.

The meeting was longer than it was expected to be.

Business was not as good as it was supposed to be.

多说两句：关于as的这种用法不太好理解，Swan的PEU中只是说很像关系代词，可以充当主语，宾语或表语。而国内的司树森教授就直接认为它是关系代词（实际上不一样，因为很多时候不能直接替换为真正的关系代词），详情请见司树森教授编写的“当代英语疑难问题详解”一书。