Is it possible to redirect more damage to a unit than what it would take to kill the unit, provided I do it on the chain? For example, I play master rune of spite or some other thing to damage all units, can I use temple guard, spend 2 resources to redirect damage from unit A to unit B and then on the chain, redirect damage from unit C to unit B and so on. Hence, when the chain resolves, all the redirected damage would land on B who would have more damage than whatever it takes to kill it?

You can do what you are saying.