I've been using these formations as a strategy with some success. In order to fit it the way I want, I've been running them outside the contingents. But that's personal taste.
I've had good success against armies that rely heavily on support elements, or have a focal power point that is not the super durable deathstars (I.e. rerollable invulnerable saves) that we see often these days.
My usage has taken full advantage of the fact our positional relays and homing beacons don't need to be on the field at the beginning of the turn to be used. One squad of pathfinders outflank with a recon drone, and both squads of stealth suits are minimum with homing beacons, also out flanking. I don't like, despite the formation begging for it, putting the broadsides and riptide in deep strike. For me, these start on the board, along with 2 squads of 6 pathfinders on a tidewall shieldline. This, I find, deters a lot of firepower from going at your precious markerlights, gives them some mobility, and rerolls of 1s to hit gives a decent hit rate. By that's more preference than anything else (personal love of pathfinders)
I agree with Vres'ka, when it lands you can really dish out some hurt. But the thing you pick here can win the game then and there, or you'll suddenly be on the retreat to keep your important strike elements alive. I have won multiple games halfway through my turn 2 shooting phase doing this.
Don't forget to apply some flexibility to your plan, not everyone will fall for the bait piranha or its drones, so have a backup plan incase some of your important units don't come in.
Experiment with it, find the loadout and setup you like. It can be a lot of fun to pull off.