For Explore farming, I’ve been using:
Mechanist Hero / Anu’s Sceptre
Bombot
Bombot
Soothsayer
Brown banner
Mechanist makes Bombot Fast, Sooth will often fill them (or a surge will), and then lights out. Anu’s is backup in case the board is being stubborn.
The trouble is troops with Life Drain, which will survive the bombs.