Hi !
After some testing, some abilities seems to have internal CD to prevent some abuse. That's good to keep the balance of the game. But as a player, it would be really interesting to know the abilities cooldown, and to have them displayed on the battle GUI.
Easiest way to have this kind of information would be to show, on the ability "button" in the GUI, a small counter or a grey zone decreasing with time.
I know that impact damage have a 30 sec CD, but it's hard to remember when it's available for each of my cav units, and sometimes, a charge delayed from 1 sec can change the tide of a battle.