My daughter is a setter (RS Freshman) at a very strong (top 20) DII college. This year the team is running what I think is a variation of a 6-2. The two setters rotate in, are never on the court at the same time and are only playing back row. The front line is tall, talented and deep.
What are the advantages and disadvantages of running this offense.
The type of offense you are describing, is what I call a front to back 6-2 and your questions usually come from a setter. A setter and a RS split the position, which each subbing in/out with each other every 3 rotations. This type of offense has grown in popularity in college because of the increase in substations allowed in recent years for NCAA (NAIA has unlimited subs). It has been a popular offense in club, because of their larger substitution counts and because it allows additional athletes to play (keeps the players and parents happy).
The advantages of this offense, is that there are always 3 attackers on the front row; it is tougher to block 3 attackers with 3 blockers, than it is with 3 blockers and 2 attackers (5-1 offense). Also, it allows for a taller right side blocker for 6 rotations; not only taller but better blocker on the right. Smaller setters enjoy this offense, because they don't get discriminated against in the recruiting process for not being tall, and RS's like this offense because 1 more gets to play each match.
There are disadvantages to the front to back 6-2. With 2 setters running the offense, there are two variations of sets (each setter has their own particulars), and it can be hard for a setter to get into a rhythm by only being in for 3 rotations. Some may feel that 4 players constantly swapping in/out every 3 rotations can disturb a certain chemistry/flow with the match.
It will be interesting to see if there is a growth in the number of programs running the front to back 6-2 offense - In the Top 10 Division I ranks, Texas, Nebraska and Washington have used the front to back 6-2, while Penn State, Stanford and Wisconsin have held with the traditional 5-1.