Secure MP doesn't grant extra attacks, it merely removes the extra miss chance from flurry attacks (like Second Shot).
I think you might under-appreciate just how much more awesome this is. Rapid Fire + Secure MP throws out 4 attacks that don't have a 65%(?) base miss chance. That beats the hell out of +1 attack that is more likely to hit a random cow on New Texas than your target, regardless of where you are.
But OP's character is clearly a Smuggler, the only class that doesn't have a good multishot perk.
Well, Smuggler gets Second Shot, which is enough to make Secure MP worth it.