The past perfect (whether simple, passive, continuous, going to, or anything else) always means that the speaker has chosen to view the event from a more recent point in the past. It is nearly always a free choice for the speaker - it does not depend on the objective sequence of events. English speakers often don't bother with it when the temporal ...
Dishwashers were introduced in 1978.
This is a very simple statement denoting the fact that dishwashers have been around since 1978 and no earlier.
Dishwashers had been introduced in 1978.
This statement is sort of weird. People would expect you to say more about the topic in continuation if you use past perfect tense. Past perfect tense is used to speak ...
"Were introduced in" gives a precise year. They were not introduced before that date.
"Had been introduced in" is more vague. It can mean a precise year of introduction. It can also mean that they were introduced in that year or earlier, although that would more commonly be written as "had been introduced by".
meaning that the Performance Department will be responsible for the previously mentioned actions
In that case I suggest none of your suggestions fits well. So I would prefer
in the event of them being the responsibility of the Performance Department
"accountable to X" means that they have to justify themselves to if there is a problem with their actions. You say "John is accountable to the Board of Directors" to mean that if there is a problem with John's work, he needs to explain himself to the Board. If "them" means "these actions" then the verb "...