this has been really pissing me off lately, on the very last turn coming out on the the main straight the kerb has a little ditch in it which can spin some cars around, see replay for example on lap 3 very last corner

Just about every real-life track has got some 'quirk' that drivers learn about from driving the track. Roll with the punches. Avoid the kerb, or set your car up to deal with it. Simple.

Prime example is the 'hump' in monaco, where drivers swerve way off the line to avoid it.