I think with adrenaline it would just add one more attack instead of it attacking the full amount twice.
So an example would be a leaf dragon who attacks four times, would only attack five times, just so its not super overpowered with adrenaline.
I also thought it would be balanced with the number of shields that stop attacks (Turtle shield and Phase Shield) while I think it helps more against Dissipation Shield and Bone Wall, because of there numbers, also, it has a terrible time against Fire Buckler, and Permafrost Shield, since they could be frozen on the first attack, While Dusk and Fog could make them miss altogether, most decks run shields, and the rush decks usually need there quantum for the creatures they put out, hence why I made it cost 4, maybe I should upgrade it to 5. Thanks for the input.