conundrum; an assault on tau piranha squadron....

so i was beating on on my tau buddy yet again this week and i had the brilliant idea to charge a squadron of piranha, after an unfortunate schmelting accident. ( plasma vs Venom... )
as the little buggers charged the piranha the tau players declares that his FD ( flletchette discharge ) goes off 3 times over as there are 3 vehicles, and declares since i have 10 kabalite warriors on the assault, he gets to roll 4+ for wounds __30 times __

now im not too sure how that assault should of unfolded, and he would not be swayed about all those being reacitve prior to me actually scoring a hit on his models.
any ideas?

The problem lies in a 4th ed codex using 5th ed vehicle squadron rules.

By the wording of the fletchettes, any vehicle attacked in HtH rolls to wound all the enemies attacking it. The problem with te squadron rules is that you attack ALL vehicles rather than single ones.

Couple of possible views...

1. as you are attacking the squadron and can affect all vehicles you must take the FD from all vehicles
2. You take as many FD attacks based on how many vehicles you are actually engaged with
3. The FD does not work on a squadron as the rules state when you attack a vehicle and a squadron is not a single vehicle
4. The squardon counts as a single vehicle and as such you only ever take the effects of 1 FD.

RAW is grey as well so thats no help.

I understand the logic behind 1. but i think 4. is the most balanced. It also means you only need the upgrade once in the unit to benefit.