Its a good point. Regardless of any stats, would you rather have Bale in the team or not? Of course you would so even if the stats said we were worse with him in the team you would ignore them.
As for the jokes about Wales having 3 teams in the PL next year (Swansea, Cardiff and Bale), well they are just banter which should be taken for what they are and not worried about. I would rather worry about Bale being hoodwinked into going for the money/glory by some mega rich club if we don't make CL than anything else.