I have seen at least corvettes and fighters idling in the midst of combat at several occasions, even in beta 3.
In large fleets, I have also seen an attack-and-idle pattern, with fighters and/or corvettes split in 2 groups, where one group moves and attacks while the other idles, then the attacking group stops attacking and moving, and the first group starts it. They switch back and forth the attack and idle roles until I set a target queue manually. That was on beta 2c, I haven't found it yet on beta 3.
