Attack increases – this can be considered analogous to damage. Defense increases – this can be considered a replacement for HP. And initiative increases. This often saves them.
Are you kidding me? Are you saying that only un-upgraded units have these stats increase, while upgraded units don't? That's a strange way of thinking. Upgrading Centaurs definitely increases their effectiveness by 1.5 times.
Горящие реки сходили с ума, пытаясь остаться водой,
Земля пропустила коварный удар, раскрывшись на шаге вперёд,
Взлетел разъярённым драконом Огонь и понял, что тоже умрёт...