I don't know about 4E, but Saga uses Fort defenses instead of savings throws. You don't save against poison; the poison makes an attack against your fort defense.
Seems like falling should go the same route. After all, it's not the fall that gets you--it's the sudden impact with the ground.
So, the ground makes an attack against your fort defense. Attack bonus is equal to the number of dice you just rolled (so, +1 per 10ft of height). Damage is 1d6 per 10', like always.
If you fall 20 feet, attack bonus is made at +2. Threatening to a first level guy with a Fort defense of 14, but not too bad. If you fall 200 feet, the attack bonus is +20. Even high level characters are in trouble. Things like spikes or other rough landing surfaces add to both attack bonus and damage. Soft surfaces like water or piles of leaves detract from attack bonus and damage.
If attack fails, you just take the damage. If attack succeeds, you're also crippled (penalty to attacks, speed, and defenses). If attack crits, you're crippled and take double damage.
So even short falls are dangerous if you land wrong (are critted), but not life-threatening: a crit from a 10' fall is still only 2d6, which isn't too bad even for 1st level characters. And long falls are scary, even for high level characters. As they should be. It's cool and fun to push enemies off cliffs, or be in danger of being pushed off a cliff. It's not fun to think "Sure, I could bull rush him off the three story balcony... but he'd only take 3d6. Meh; not worth it."