I have two suggestions:
1) Already make hero skills work like on official - hero UD, berserker and valor share same cooldowns.
2) Make all five hero skills share same cooldown.
1.How works first u can see here:
When he presses hero Bers, UD and valor goes into cooldown.
2.Why i suggest second? So in mass fight as well as small scale pvps heroes should think, what is better to use - Berserker and kill all, valor and help clan members, hero UD and tank and so on.
Discuss?