This should be a point for errata.
There are 3 levels of hazards in the task system; safe, normal, and hazardous.
Fateful merely means that a failure guarantees a mishap.
A failure on a 'safe' task means that any mishap is 'superficial'. This is specified in the section for 'safe' tasks.
A failure on a normal task means any mishap is 2d6 ( 'minor mishap' )
A failure on a hazardous task means any mishap is 3d6 ( 'major mishap' )
Now that would make more sense except that I note in the Referee's Manual, "Safe: With safe tasks if a mishap occurs, it is never damaging." Ergo, while there can be a safe superficial mishap, the referee would have to find some consequence other than damage. The revival role is not specifically described as safe, ergo by your explanation the 2D6 roll for mishap applies, with potential damage ranging from 1d6 to 3D6.
Now here's a question I couldn't find an answer to. The wounds section deals primarily with converting combat "hits" to wounds taken by your stats. Revival roll damage is, presumably, wounds rather than hits. So, is it 3D6 against one stat and dump the excess, or overflow onto another stat, or three 1d6 rolls against random stats (St, Dx, En)?
Starship Operator's Manual (a DGP publication, but heavily relied on) calls low passage "not any more risky than middle or high passage when there is adequate medical expertise on board," but that might be a bit of an exaggeration if 1 in 12 passengers is spending the next few days after revival on bed rest. Imperial Encyclopedia (not a source I think of when looking for rules, but nonetheless full of them) clarifies on Pg. 87 that a superficial mishap on revival is 1d6 wounds for 1-6 days, after which healing is automatic except for some pallor for 1-6 weeks; minor mishaps are 2d6 wounds for 1-6 days with mild motor impairment (-2 Dx) for 1-6 weeks; and major mishaps are 3d6
permanent wounds with medical diagnosis and treatment needed "to restore
full health."
(Which means what, that the "permanent" wounds are not permanent? And 1 in 144 low passengers end up in the hospital with these "permanent" wounds. Not so bad as CT, but certainly more risky than middle or high passage. Me, I'd replace the Low Lottery with a waiver agreement limiting damages to the cost of passage - i.e. the hospitalized passenger gets a refund. Costs the captain roughly Cr 7 per passage, which is pretty close to what the Low Lottery costs. Except, Errata clarifies, "Refunds or civil liability if a low passenger fails to survive the trip are not allowed." Uh, how do these rules result in a death? I'm not even clear that it's possible if one of those 1 in 144 is luckless enough to run into a major mishap during medical treatment - although you could end up with an unplayable character.)
Clearly the rules are poorly written although the system itself is the cleanest ( imo ) of any of the editions.
It's clean if you can get some experienced player to help you work through the poor writing - on which subject I'd say thank goodness for this forum and folk like you, or I'd not have even bothered with the system.
add: Ooh, saved from an accidental double post by some new 10-second rule. Nice addition!