Mass Effect 3.5B: Taste the Rainbow (Story and Ending Discussion; Spoilers!)

[BRC]

To be fair, that kind of thinking is different enough from the krogan norm that it could be indicative of a lack of Blood Rage. While there's no way for Eve to know of any genetic deviance (unless Mordin told her in passing), the ME wiki doesn't list "Rage" as one of Wrex's powers in ME1, and there's not much in favor of its existence in Wrex. (In Favor: "I AM URDNOT WREX AND THIS IS MY PLANET!", "When his fury is unleashed, it is a terrifying sight"(ME wiki); In Disfavor: the fact that he "rarely loses his temper" (ME wiki), his competent leadership of Clan Urdnot; Grunt's static power "Krogan Berserker" specifically states his blood rage, while Wrex's doesn't; can go either way: "Rage" is only listed in multiplayer Krogan.) Besides, it's in character for Eve, especially since she's virtually the only krogan (male or female) who sees the problems ME1 Wrex did (and ME2 Wrex began to fix).

Rarely losing his temper and competent leadership are signs of a strong will and intelligence, not a mutation.

According to the Codex the Blood Rage is caused by a quirk in Krogan Biology where Adrenaline suppresses Serotonin, so a Krogan who starts to get Angry (Adrenaline) will have lots of trouble calming down and will become increasingly aggressive as the Adrenaline flooding their system switches their brain over to Fight-Or-Flight (Who am I kidding, Fight) mode. After the Krogans nuked Tuchanka, scare resources meant that Krogan WITH this mutation did much better, since their adrenaline-flooded systems could fight longer and harder. When you consider the Pre-genophage Krogan breeding rates, it's easy to see how what was once a rare mutation became commonplace (Those without it are killed or driven away from resources by those who have it, with access to resources the Blood Rage Krogan are able to breed, passing on the gene to their many children)
I think it's more likely that Wrex is simply strong-willed enough to force himself to calm down before he gets Drunk on adrenaline and does something he regrets, rather than anything genetic. The Blood Rage dosn't cause Krogan to lose their temper, it just means that, when they do, they get very violent and stop feeling pain. If Wrex is unusual, it's because he can fight that instinct and approach situations logically.

Wrex isn't a Krogan X-Man, he's Krogan Batman.


Edit: Concerning the Krogan Birthrates, it actually makes sense that the Salarians would make that mistake. Salarians have no sex drive, and consider reproduction a biological necessity rather than anything else. They had their math right, they didn't know their xenosociology. Maybe because they did not actually intend to use the Genophage when they made it (That was the Turian's decision), but they didn't realize the impact it would have on Krogan society.