Hi there,
The fact you only need a 'slight improvement' would suggest that you should try again. Next time you will know exactly what is coming (I've done the tests twice and they were very similar) and hopefully that'll be enough to get through.
Waiting 12 months is a pain in the derriere but if you're serious then it's not THAT long. That's the thought process I went through before deciding to reapply.
Good luck my friend