Staining wood and dark absorbent spots giving a rather blotchy outcome has been problematical from the time man started colouring wood with stain. To try to improve things I do use an old school method to reduce darker patches becoming to obvious. To start cut the stain by 50% with it's solvent then working quickly go over the wood with the same solvent, this will lower the woods absorbency especially in the high absorbency patches then apply the cut down stain also working quickly then let dry. Keep working this way strengthening the stain mix until you obtain the depth of colour you require. It is a very simple method and with a little practice in not going over the more porous parts of the wood to many times with the stronger stain mix less darkening of the porous patches will result.