Spawn locations are indeed terribly wrong in the Hoth level.
At a certain point, the rebels will only spawn from inside the hangar, which is at the same time when 2 of the hangar entrances can be attacked by the AT-AT. This means that rebels can only leave through one single and very narrow entrance, so they just die like lemmings towards a cliff, specially because all A/X-Wing powerups can only be caught outside.
The game is indeed terribly unbalanced. The Empire has two "invincible" AT-ATs that can call airstrikes every 45 seconds, two AT-STs that can grind troops under cover because its laser blasters have splash damage and a mortar attack. The Rebels have no ground vehicles and their ground turrets (which the Empire can also use..) are very fragile and overheat way too fast.
Air vehicles are a bit more balanced, except for the Rebels' Airspeeders which have terrible maneuvering (limited pitch, slow yaw) so they become useless as soon as TIE Fighters/Interceptors are in the terrain.
The heroes are both useless in an open space because they have no decent ranged attack so they're killed within seconds - and most of the Hoth level happens in open space.
Yeah, the game has many flaws and the arcade-ish part of it (random terrain power-ups, teleporting to vehicles, non-selectable spawning points, etc.) is what hurts the experience the most.
But at the same time, it's by far the best Star Wars experience there is.