Rage spent is zero? No chest digging whatsoever? Is this the trade off when using solo BKs since they are so slow?
I really don't understand why they should go "boring" solo. Why not use some support troops? At the very least you could add Bone Dragons to fetch for chests since whatever build you have for BKs would most likely benefit the undead dragons as well (Eviln, Staff of the Acolyte Necromancer, "Dark Commander", etc.).
Even if you add slow troops like Inquisitors, Gorguanas, Archmages, Demonologists, etc. you could always get the blue pet dragon. With "Dark Commander" level 3 you would have +2 initiative, an additional +1 from the blue pet dragon, and your Bone Dragons would most likely give you the first move. Then just Teleport level 3 your BKs to the enemy ranks.
At least this way you still get to fetch chests.
Btw, the best way to get Black Knights is via the wanderer scroll Call of Death. I'm still at the first 4 islands and I already have 9 wanderer scrolls, 2 of which are Call of Death.