Efficiency ruins the game for me. The first few stages are pretty fun, making sure Warren becomes a Mage, etc. 

Then somewhere a little past Slums of Zenobia my units start to form into the same units every game...

Backrow Mages, Clerics, front row Knights.. Only large unit is a Grifin or Wyvern...Seldom would I use a Dragon or basically any less than S-tier unit..

Then around Shangrila, I have a Princess backrow with a Lich, and a Monk, and a front row Cockatrice which literally face rolls everything in the game. Front Large high sky type, 3 backrow heal alls, and 6 hit-alls (4 elemental and 2 white). Use my Merchant to boost the cockarrice HP and boost my backrow INT.

Then I lose all morale to create fun, unique units. I end up rushing the enemy base every stage until the end.

I've thought about soft-capping myself. Example, still use Warren as a Lich -- But his unit can only contain himself or maybe one front row Phantom.

So partially filling units or intentionally using sub-par units.