Generally speaking, all the raid buffs are active during the opener window.

Rook Overdive is equivalent to 10 attacks front loaded. This means in isolation, Rook Overdrive is ten turret auto attacks (About what you lose for the 30 second downtime).

However, during the opener, you have every single raid buff going. Trick attack, hyperdrive, brotherhood, etc.

So it's 800 potency x all multipliers, which is more than you would get with 10 auto attacks over 30 seconds. It will also be a large DPS gain if you do so before an invulnerability window.

And if you roll a DCrit, it's like having 10 full DCrits.