I think the answer is no, but...

Can this card be played in response to bonus strikes from a battle back?

The answer is...yes!

One of my favorite cards in the game. Played at the right time alters the game every bit as much as a cleric spell

Yeah... and play after the opponents dice roll ! Its nice "in your face" card, not like clerics kill-all-spells-cost-7-lores

I do appreciate your jesting (evidenced by my doing the same thing in the post above ), Alistaja , but I did want to express something a little more earnestly about these points: One of the aspects of the lore decks I appreciate (and could be talked about as "balance") is how the certainties involved in different cards affect their play value. Backstab gives a certain amount of hits that will be taken from the defending unit and applied to the attacking one after seeing those bonus strikes for hits rolled. Hills Rumble gives a certain amount of units that will be affected and a certain amount of dice that will be rolled depending upon opposition's position upon the board - but no certainties about figures removed from the board. A card such as Evade gives one a certainty that as long as an escape path is kept open, a particular unit will suffer no damage (and the potential for leaving a unit that had planned on a gain ground movement for defensive positioning will be left in the lurch ).

I really enjoy the interplay of the various cards in this manner, how their values shift according to the action on the board.

Now I can feel confident in my victory. There was no complaint during the game about the use of said tactic. However, when I was reading the card several hours after the game, I wasn't so sure.

Another cue about when a card can be played is on the card itself: cards that have the lightning bolt insignia upon them in the upper left of the text box are able to be played on either players' turns, during the turn phase indicated on the card. But maybe where you felt there was room for interpretation was in the use of the words "attacking enemy unit". I'm pretty sure that the rules are consistent in referring to units that are ordered and then roll dice during combat as "battling" while any unit that is rolling combat dice is considered to be "attacking", whether it be as a result of battling or battling back. A bit fried from work today, but I think that makes the sense which I intended lol