All the races have at least one type of structure or person who can heal others. For example, the Humans have the Priests, the Orcs have the Witch Doc

One thing that some people do is hold back on the hero abilities. That is the worst thing you can do, so always make sure that you are using the most of the abilities you have at your finger tips!

Also, you might want to put them into something that might be extremely useful later in the level, except, perhaps, the most powerful skill that any hero can achieve, or ultimate skill, at level 6.

The others have three levels of effectiveness, but are all useful in one way or another. Spend them wisely... how you use your hero can change the course of the game.