I hope I can express myself well, what I'm suggesting is simple.
1) put 3 instead of 4 unlockable abilities during the game;
2) give the possibility to choose a passive ability (only 1 passive ability can be used) that will be already activated at the start of the match.
Obviously heroes who not very useful passive, will be balanced with very strong unlockable abilities.

Why this idea? Because I believe that heroes with many active passive skills have a great advantage than the other players, (see conqueror who can heal by parrying or warlord who dmg even if U parry) what do you think?