Okay, my new missile rack arrived, and I've had time to do some testing. Here are the results.
The Stats can be seen here:
Enzyme Missile Testing
So my basic testing procedure is, I deploy a Taipan fighter with the shield disabled, and shoot it with the enzyme missile, then count how many seconds it takes to die.
Test 1: Standard Enzyme Missile. Fighter died in 27s/28s. This translates to 45 base hp – 7 impact damage(5*1.4 for explosive) = 38 hp in 28 seconds, or 1.35 damage per second.
Test 2: Old Modified Enzyme Missile. Fighter died in 25s This translates to 45 base hp – 10.5(7.5*1.4 for explosive) = 34.5 hp in 25 seconds, or 1.38 damage per second.
Note: Slight differences may be recording errors. Additionally, Enzyme Missiles do degrading damage. They do about half their damage in the first 20 seconds, so the slightly higher damage per second is purely due to dying slightly faster, because of the slightly higher initial impact damage, and NOT because the caustic burn is actually higher.
Test 3: Both missiles at once. Maybe the different dots can stack. Fighter died in 20s. 45-7-10.5 = 26.5. 26.5/20 = 1.325
Test 4: 2x shots of modified launcher. Fighter died in 18.5 seconds. 45-21=24/18.5=1.29 damage per second. No stacking.
Conclusions
Now, the juicy part. Is the NEW modified launcher any different?
Moment of truth: The new missile rack kills the fighter in……… 25 seconds! Or 1.38 damage per second. This is identical to the old rack.
The new missile rack does NOT penetrate shields.
The new missile rack does NOT stack with itself.
The new missile rack does NOT stack with the others.
Conclusion: The new missile rack is identical to the old modified missile rack.
Analysis of Effectiveness in Combat
It does approximately 3.75 DPS to shields, and with constant fire, approximately 6.63 DPS to armor. Even assuming the target has 50% resistance to explosive damage, you're still looking at a standard C1 missile rack doing 12.5 DPS (plus heavy module damage), compared to about 4 DPS from the modified enzyme missile rack, which is also incapable of damaging external or interior modules.
For context, that's about 66% as much damage as an unengineered C1 gimballed multicannon, which also cannot be shot down by point defense, and is capable of damaging modules.
You would need to be hitting the target less than once every 14 seconds for the Enzyme Missile Rack to become superior, against a max-engineered target.