I've played Descent probably about 8 times now and all of the orders seem to have their place, except for Aiming. The only situation where it seems like it would possibly be useful over Battle would be if you a high amount of armor to overcome, and your hero doesn't deal an overwhelming amount of damage. And usually by late game, most heroes would normally do plenty of damage, so they would rarely be inclined aim.
I'm proposing three possible changes to how the hero's Aim would work. I'd like to see other people's opinions of each.
Option 1 - Player may change one die rolled
For an aimed attack, the player would roll their attack die. Then they have the option to change one die to the side of their choosing. Most often this would be used to ensure that you don't miss. But in the event that your roll didn't miss, changing one die would usually result in 1 or 2 more damage or range.
Option 1b - It costs one fatigue to change a die (maybe with a limit?)
Option 2 - Double the effect of black die
This would be stronger during the early game but weaker towards the end. You get more bang for your buck spending a fatigue on a black die. Thematically, the more skilled you are with a certain type of attack, the bigger benefit you'd receive from preparation and focused aiming.
Option 2b - The player still gets to do the standard re-roll.
Option 3 - An Aimed Attack gets 2-4 free surges.
The number would be just based on what would seem balanced.
Early game it takes multiple surges to get a boost to range or damage, so the effects of free surges wouldn't be overpowered. By late game, the extra surges could be quite powerful, perhaps reason enough to choose to aim rather than battle.