First of all, he needs time.. Not everyone understands it in 123.. We have people in our guild that need several wipes to understand a fight, we have others that understand it while it's happening..
Second thing is, there are people - like you say - that enjoy numbers, if he enjoys playing on the AH, why not? I'd like to have bit of his skills of the AH..
If you take him to heroics, if you keep explaining - yes it will be hard, I have to do it aswell to the trials in my guild, you'll get annoyed and stuff.. - he'll get it and he'll improve. Don't go flame on him that he's doing all wrong, just suggest things and tell him to try it out several times, it won't work from the start no..