My wife and I stopped playing IA because we fought when we played. Last night I had a friend start Descent (at his request) and I think we had fun, but we had a VERY frustrating two losses due to the same thing that made IA unwinnable (IMO) as the Rebels. Focus Fire!
So when my wife played as the Imperial, I felt that a wise Imperial always focuses ALL their fire on a single hero, who is unable to do anything to prevent this. Same in Descent. Without time limits, the heroes can hang back and rest, killing enemies more leisurely. But with time limits, they have to balance move, attack, and rest. I think nearly every mission can be won by the Imperials by simply clogging hallways and focusing on a single hero until they are wounded.
The mission for Descent last night had us chasing after the boss as she tried to escape, with monsters and a series of closed doors in our way. One of our characters had a good attribute for opening doors, and had the equivalent of 14 health. She had a potion to regain health, a talisman to give her extra defense, and an ally who could give her extra defense. The overlord (me, I play as both OL and two heroes in Descent) moved monsters in front of the doors two layers thick, forcing the heroes to thin them out for her to get up to the next door. This placed her in a precarious position each turn, and with 5+ attacks targeting her, she got knocked out each and every turn.
I feel like it is unrealistic for three squads of stormtroopers to be presented with a Jedi, a Wookiee, a guerrilla fighter, and a smuggler, and have all nine stormtroopers ignore the other three to shoot at the smuggler until she is dead. We have been tossing around the house rule that "If there is more than one viable target, each deployment group must target a different hero." But I can see this being a major power-swing.