I understand the difference between damage value and attack and wrote very specificly attack. My point was that your Attack value vs Oponents Defense value decides what % bonus you get to your Damage value. Since the relation between any positive value (like 1) vs 0 is infinity I asumed infinity would be enough to hit the 300% cap. I'm still not sure though if the damage will be 4-6 x 3 or 1-2 x 3 +3-4 (- is range not minus here).
Anyways, a picture says more than a thousen words and three pictures makes everything very clear:
(dragon arrows don't work on thorn-hunters)
(the black dragon stack crit me for 16k and killed the entire stack before they got a chance to act in the first turn)
(normal hit on the low side with lvl3 dragon slayer on, enough to devastate all dragon stacks)
In conclusion I think they'll be fine without dragon arrows which is nice but will probably need some babysitting.