I've always believed that if you want a solve to be successful badly enough, then it will be successful. As an extreme example, if I said I would give you $1,000,000 if your very next BLD was successful, I'm pretty sure you would win that bet. Think about how you would approach a solve like that. Really, stop for a second and think about it.
I do public demos a lot for 3x3 BLD, and I have a much higher success rate for those solves than I do in competition. I've done solves everywhere from at a bar with friends all the way to as the official speaker for a Pi Mu Epsilon induction at a University near me. The secret to my success rate in these situations is to g...o...... s...l...o...w....l...y and be very mindful during the whole process. Being mindful means to remain highly focused on the task at hand.
Ok, so to improve your competition success rate (to get a fast average of 12) you still need to go quickly, but have confidence in your ability to get the next solve. On each solve be very mindful during the whole solve (it will feel kinda like you turned your brain off of economy mode and have started burning the nitrous). Your brain should feel tired after a successful average of 12 from remaining so focused for an extended period of time. Also, go very slightly slower than your full speed. The best way to describe it is relaxed-fast. Memorize relaxed (but still sorta fast), then solve FAST (but still sorta relaxed, i.e confidently). Make sure each solve is just slow enough to still be fast, but you still feel fairly confident that you're gonna win my $1,000,000 bet on each solve
I have gotten a fast (for me) average of 12 in 5x5BLD using this mindset, so from personal experience this does work.
If you practice solving this way, I have no doubt that you would get a successful average of 12 soon, and one that is not that much slower than your global BLD average.