Translation: 'Overwhelm'
As a native Chinese speaker who is learning English, I have the same problem. And I don't think there is word in Chinese similar to overwhelming. The solution I came to is change the expression completely depending on the context. So here are my tries for the examples:


It was a bit overwhelming to say the least.


  再怎么说，这也有点太多/过分/严格了
  
  This translation really depends on what the subject is. If it is something too much, use 太多, if it is something too went too far use 过分, if it is some overwhelming requirement use 太严格.

The work seemed very overwhelming at first.


  一开始这个工作可能有点难以应付/这个工作可能压力很大。

The situation made me feel overwhelmed.


  这情况让我压力很大。



P.S:

Similar as overwhelming, I couldn't find the word in English for 过分 in sentence like 你太过分了!.

It means "you went too far!" or "you are way cross the line here!" but both of them seemed too civilised for the original tone since the Chinese one can be yelled out at a raging scolding tone and contains strong personal opinion but both the English version seem to be too fact based.