Actually, all you need are transports with "capture planet" strategies.
With the fleet set to break formation, those transports will definitely be trying to capture, and all the warships will oblige them.
Not long ago, I attacked an enemy homeworld with a three-pronged attack.
Two troop transports came in from the left sector, two from the right sector, and my warfleet came down from the top. (All on the same day, for a single combat)
The enemy fleet ended up in a wall formation facing to the side, which gave my warships a great flanking position at the top of the "T". The battle raged, and the troop transports swooped in from the sides, taking only a few hits before dropping about 500 units on the planet.
Almost all of my ships were crippled, but not many were destroyed. Quite a nice result, for what I was originally expecting to be a suicide mission against superior numbers
BTW; with break formation, my missile ships got to stay back and lob, my torpedo boats got in and slugged it out, and my PD ships ran around chasing missile packs. Every ship got to fire at their own best targets, and move to the proper range for their guns against that target. Staying in formation, even with small sub-fleets would mean lots of ships moving to sub-optimal positions in order to stay in formation.
I don't want any of my missile boats getting too close to the enemy guns, and my gunboats and PD ships need to hound their targets closely.
By the end that single warfleet had collected 2% experience (starting from scratch); all the ships will benefit from that in the future, and all the warships will contribute to increasing it (even though they are breaking formation, they are still part of the fleet)