Yes, only when troop totally left in barracks. Little uncomfortable, but no more. I had reserves on mail and ready for gathering troops in barracks.
And i have not changed my troops for event. Too expensive to do it only for this.
As i said, i was only 1 week in the game. Lately, at end of event, i did ~50k damage with "empty troop" tactics. And damage reflection was only little piece of this, sure.
Sasaki Kojiro with Elite Crimson Riders did ~16k dmg with first strike (4,5-5k base attack), The Tiger of Kai with Elite Black Riders did 4k+(4-10)k, Honganji Kennyo with Heavy Artillery did 5-10k.
Uesugi Kenshin and The Dragon of Echigo did 3-5k, and only 1-1,5k with damage reflection.