Reprisal has only been around since Mechakolos release, that was more recent than a year ago I'm sure... Reprisal can't be the only explanation...
Perhaps with recent power creep it's just getting too hard for the staff to conceptualise playable Backlash cards, I can't remember the last one I saw in play except occasionally Cortez ...
Backlash may be too gimmicky for the staff to create more of. Stop cards outclass them against SoA and aren't bad without. Compare Sprinter to Cortez: against SoA, Sprinter can KO (with one less damage) in situations that Cortez can't and, without SoA, Sprinter is still one life gap short of Cortez for a whole star less.
Abilities are what make the (UR) world go round. SoA is considered the most powerful ability/bonus because it robs your opponent of this most valued element. Also, with cards like Derby Queen and Noctezuma, Reprisal is showing how dangerous it can be compared to it's counterpart Courage.
@TDB: comparing Stop and Backlash is intuitive, since cards with both abilities get stronger when facing SOA. I don't think it tells the whole story, though. For the example you provided, Sprinter vs. Cortez: in ELO, Cortez can be a KO threat with practically any combination of cards, regardless of SOA, whereas Sprinter needs to be matched up against SOA to threaten a KO.
Furthermore, Cortez's backlash can be worked around through smart play or good matchups-- it doesn't matter if it fires off against a Freaks hand, since they're aiming to land around 3 life anyway, and it certainly doesn't matter if you can score a KO. This is what I was talking about-- by having cards with a tremendous upside (in Cortez's case, constant KO threats) and a drawback that's troublesome but not crippling (*cough*Uchtul *cough*), you can open up a lot more tactical and strategic choices. I would love to see more cards in this vein, or possibly cards with a tradeoff ability (e.g. +2 pillz, -2 life min. 2, or Defeat: +4 life, -2 pillz. min 2)
I'm not counting it as damage reduction, I'm counting it in terms of Life Gap.
I'm not saying he's a bad card, I'm just saying that Backlash cards have an uphill battle for player attention. Cortez can get away with it because of his perfect stats and 2hko threat, but the others are lacking. And strategy-requiring cards are typically the ones that get cut in favor of versatile or direct ones in most players' decks. Stat copying cards, like Shizawa and the original Noctezuma, also take this kind of heat.
Uchtul 8/8 with SoB. Can self ko. Even though his only ELO competition is Ozzy at the moment, people still won't touch him.
Raquel is an 8/4 2* star. Sounds good, but other clans have 8 power 2* that don't rely on their bonus or have backlash and losing pillz is something that people HATE. Some people would rather waste large amounts of pillz on a single move then let their opponent take them away.
Gork has self-poison, which is the easiest to avoid, but can only have it be stopped by 5 clans. He competes with XU52 and Wardom.
Beef is in the worst position of all Berzerk backlash, the 4* position. Look at all the power that he's completely outclassed by.
Sylvia Ld only has 6 power to her name and Uma can deal as much damage with 7 power.
Bernie (8/5) is forced to fight Melanie (8/4). Her protected power is much more appealing and SoA resistant against all but 3 clans.
Norman runs into the same Pill problem that Raquel does.
I made a deck that is very good at Elo
A backlash card competes with cards in the same clan so they always have the same bonus. The only way a card can compete is through stats/*count and that really limits what you can do - and especially limits what you can do without making the card either OP or unplayable. The biggest drawback of having only stats to work with is that unless you have SoA you'll run into DR and then you're pretty much screwed (this is why I win pretty much and match against Cortez and consider him rather unplayable).
Having said that I've used Gork a lot and he's probably my favourite GHEIST 5* (Mechakolos is a silly card). You pretty much can't answer him with a DR and then his stats actually mean something. Uchtul would be a great card, but all it takes to make him rather pointless is an Arthus. Beef is both bad against DR (yes 2 are unreducable but 5 aren't and who DR's for more than 5?), so is Sylvia, Norman isn't bad, but I'm probably looking for utility in my 3*, Raquel isn't bad but needs to pill to beat att manipulators for not nearly enough gain.
Backlashi simply isn't used in ways that would make it bring an option to the table. An 8 base power Banger, and 8 base power Rescue... An 8/5 2* pussycat. An 8/6 2* Freaks - these things look stupidly strong on paper, but DR kills them, backlash costs them, and they have to pill to win against Att manip. The only way for them to be used, like pretty much any card, is to be the very best at their slot, and this is really difficult.