Substitutes: What are your thoughts on it?

[Herby]

I've finally defeated the quest hero required to unlock a substitute in the Beta version.
So, how will this new feature change the game?
Any thoughts, comments, suggestions, or strategy insights?

- The substitute automatically replaces the first hero in a fight that dies
- It pops up in the same place in formation that the hero died in.
- Also, the substitute needs to have its own runes and equipment.
- The substitute doesn't attack the round it pops in. It attacks in the next round.

These are what I've observed so far.