if you look at a chart with stochastics, you can see how many times it gives false signal. you will need a lot of 'experience' and subjective judgement calls to make the 80% success rate. In that sense, what do you even need the indicator for? anyone what has been trading a few months can look at a chart without any indicators and tell if a thing is overbot or oversold.
I have been doing intraday trading for a little over a year and would like to share some experience here. For conventional TA to work well, you will need a lot of 'conventional' participants in the market. Back in the internet craze days and the year-end bear market days, there are tons of dumb money in the market, and therefore playing breakouts/breakdowns worked really well. In the recent months however, after much of the excess is cleared out of the market, these breakout/breakdown patterns don't work well anymore. To do good, you will have to identify the major participants in the market and identify their behavior.
There is no single TA tool that will win all the time, especially those 'canned' indicators you read from a book. The trend-following ones will lose a lot of money in range markets, the range indicators will lose a lot of money during trending markets.
Trying to identify what type of market we are in, this is where experience and subjectivity come in. And if you are not in tip-top shape mentally and physically, you will be wrong and lose a lot of money.
Therefore, having your own '100% mechanical' system is neccessary for some people (me included), without those canned indicators.
It will be helpful to do lots of back testing and check if your system is sound, in terms of performance and maximum drawdown.. and that has been where I put most of my spare time lately. And yes, There are some systems can be developed with reasonable drawdown so that you can still stick to it during tough times. At least for myself, this will be the type of trading I will be willing to do in the long run, in an enjoyable and stress-free fashion.