The issue is to do with the way that air-power rapidly becomes abusive with increases in range and firepower since there are limited units that can deal with it.
Marauder is a bomber and a single, somewhat fragile unit. The lascannon can be used for AA, but only in defence, and 45cm is a 'reasonable' range for ground attacks by Bombers. However units that are Fighter Bombers can also use their AA to attack other aircraft, and here the 45cm range AA becomes abusive because it reaches out past all other aircraft AA (except one . . .)
45cm ground attacks are similarly abusive because it allows the a/c much more latitude in avoiding ground-based AA, so it could be argued that the Avenger Lascannon should be reduced to 30cm all round.
Ideally the Marauder (and Helltalon) should have a separate statline restricting the AA to 30cm, which complies with all the other stat lines in all other lists keeping the game balanced. Sadly the Marauder is highly unlikely to be changed, though that has very little impact because it is a bomber. However the Helltalon really needs to be changed to avoid the continued references to the precedence that it sets - (although this thread had not got that far - - - yet

)
So, to remain 'balanced' with respect to other aircraft, the Avenger stats probably ought to read
Avenger Strike Fighter
Type: AC: Fighter Bomber
Armor: 6+
CC: -
FF: -
2x Lascannon - Fixed forward arc - 45cm 30cm AT5+
. . . . . . . . . . . . . . . . . . . . . . . . . 30cm AA5+
Avenger Bolt Cannon Fixed Forward Arc 30cm 2xAP5+/AT5+
Heavy Stubber Rear Arc - 15cm AA6+
Also, two a/c for 150 points is far too cheap given that the two a/c can produce 2x AT hits or equivalent, twice that of a flight of TBolts, and with slightly better AA as well. The issue being that this allows 6x cheap, and very effective formations in the standard 3k 'tournament' game that can use their 45cm range to stand off from most ground based AA taking pot shots at any vehicle.
I strongly suggest starting at 275 for the formation of two, dropping to 250 or just possibly 225 depending on play-test results.