Word Choice – ‘In Cases When’ vs. ‘In Cases Where’

The where-clause is a separate clause. There is no rule of grammar that requires a comma there or forbids it. You can use one if you like. But sentence #1 has some grammatical errors that you should attend to.

You write ...interested to work...

An article would be idiomatic: "with an excellent reputation".

In a sentence like, "This bias may not be acceptable in all scenarios, especially where/when recall is important," which of where/when should be used?

Let's diagram. (partial for the sake of brevity)

This bias | may be acceptable | not | in all scenarios | especially | where/when recall is important

This is a Complex Sentence with one main (independent clause) and one subordinate (dependent clause).

Main: This bias may not be acceptable in all scenarios [notice that this main clause can stand alone as a complete sentence, which is why it's call an independent clause]

Dependent: especially where/when recall is important [the bias may not be acceptable for reasons, one in particular involves "recall" and this adverb dependent clause modifies, like an adverb, the verb phrase "may be acceptable" (negated, made negative by the adverb not) to show and answer "When?" When is it not acceptable? When it involves "recall" (whatever recall may pertain to). The adverb especially modifies the entire adverb dependent clause because the clause acts as a single part of speech, an adverb: Not just when, but especially when

Where. adv.

: act or in what place

http://www.merriam-webster.com/dictionary/where

In this sentence when is used as a subordinating conjunction.

When. conj.

:at any or every time that

http://www.merriam-webster.com/dictionary/when

Plugging in the definition of when...

This bias may not be acceptable in all scenarios, especially at any or every time that recall is important.

CORRECT:

This bias may not be acceptable in all scenarios, especially when recall is important.