Actually that's the point. The Barnett formula only gave back to Scotland some of the extra money that was raised in Scotland from oil. Until 2014 Scotland had been sending more per capita in tax to London than it was receiving back in extra spending every single year since at least the early 1970s.
See this table that shows higher tax receipts per capita in Scotland compared to the UK for the last few decades.
http://www.gov.scot/Resource/0041/00418381.pdf
Only very recently has this trend changed. London has not been sending Scotland money, it's been the other way around.
The idea that London will send Scotland extra money indefinitely despite falling tax revenue from Scotland is a leap of faith.
In fact London politicians have stated the opposite: that Scotland in future needs to raise its own taxes to cover spending.
So I ask again what makes you think London is going to send extra money to Scotland for decades to come?
Leap of faith? The UK government is responsible for all areas of the UK, whilst Scotland, Wales etc indeed are nations they are still under the responsibility of the UK...they are not going to knacker up a whole area of the UK they are responsible for. UK government sees Scotland, Wales just like English county's really...we are one big family.
It is a bigger leap of faith to hope, guess etc that leaving the UK will be better, there are no facts to indicate that will be so. The facts seem to force us to come to the conclusion that life would be much harder if we went it alone.
So at the moment I choose the less of two evils so to speak.
The fact 45% of our nation choose to ignore these points and "hope" it would be better independent is quite frankly embarassing.