As for Tazar, I have a different setup and similar actions to yours, only I eliminate the group of units and move the lizards to the lower left corner.
For Vestan, I use 25 lizards and 40 gnolls, and for Tazar, 20 lizards and 40-50 gnolls. I tested it under these conditions.
However, Vestan can manage with just 20 lizards, and Tazar with 40 gnolls.