From the way I see it, it's less about the number of actions per turn that you have and more about how impactful an action you take is. Yes, your amount of actions per turn won't change as you level up but the versatility of your available actions per turn will, plus your base actions are only a part of it, since reactions, synergies or other tactical maneuvers play a huge part as well. But to be fair, there is little of all this in the game, since we are just talking level 1 to 4 here and a lot is still missing or poorly implemented as of now.
