Looking through the logs of the review queues, I sometimes see very long chains of reviews from the same user, frequently all with the same decision (leave open, no action needed, looks OK, etc.); occasionally, these take place over very short periods of time.
For example, in the First Post review, I have recently observed a user make $17$ reviews over the course of $1$ minute and $9$ seconds - this is an average of about $4.7$ seconds per review. Looking through the history, I can see other periods of rapid reviewing from the same user ($5$ reviews in $24$ seconds, $3$ reviews in $11$ seconds, $3$ reviews in $5$ seconds, and so on). The vast majority of these reviews select "No Action Needed." These chains of reviews include at least one passed and at least one failed audit, but also contain "No Action Needed" reviews for posts that were later closed / deleted via other queues.
In my experience, $5$ seconds is too short a time to make a reasoned judgement about whether a first post is good or not, and since a single "No Action Needed" removes a post from the queue, inattentive first post reviewing seems to be more potentially harmful than other reviews.
I have seen similar behaviour from other users in other queues, too - including vastly more egregious instances of robo-reviewing.
Now for the questions:
How fast is too fast when reviewing (am I just a particularly slow reviewer, or is $5$ seconds sufficient)? If one observes scattered instances of such reviews, what is the appropriate action (e.g. flagging the moderators with a report)?