But, since there´s no icon to mark that a unit has a hero (besides the one that appears on deployment screen) and, most important, the bonus values doesn´t seem to be added (at least visually) on the unit stats, i found quite easy to lose track of the advantages a hero is currently giving to the unit.

I think the game needs both an icon to notify a hero is present and also resalting the bonus attributes. It could be as simple as adding the bonus to the base value and mark it in green, for example. That means it´s an altered attribute due the presence of a hero in the unit.