Do all races flaks do this? Like Advent defenders?
yes, if you like I will compare illuminator vs defender.
dps:
illuminator hitting 3 defenders will do 15.6 dps (5.2 dps per beam).
defender hitting 4 illuminators will do 22.2 dps (5.55 dps per side).
cost and supply:
illuminator costs credits 350, metal 50, 40 crystal and 6 supply.
defender costs credits 350, metal 40, crystal 20 and 3 supply.
hp shields and armour:
illuminator 500 hp, 500 shields and 2 armour.
defender 650 hp, 620 shields and 3.5 armour.
range (however Im sure both players will move close to each other to get maximum amount of beams..ect):
illuminator 4800.
defender 3000.
the reason no one spams only flaks is due to the reason that they are only good vs siege, fighters/bombers and LRM (assailant, illuminator, LRM), but not too much vs others. If your opponent is only spamming LRM, adding flaks
as part of the fleet and not the whole fleet will help a lot.