Macdo has hit the nail on the head.
Cardiff's problem is simply that right now no carrier has enough belief in the presence, resilience and non-seasonality of the market to risk considerable sums of money to start a base, or even routes, from there.
All the chest beating in the world on WAN, or anywhere else, won't alter that fact - the only way that airlines are going to get interested is if (a) their other, local, bases start to face massive capacity issues (not for a while, that one), or (b) the WG starts putting money into the pot massively (of questionable legality, not sustainable and potential political suicide in a time when pensions are under attack), or (c) considerable effort is put into real, empirical data collection and research as to how big the market actually is, to prove it is there, and to go and tell the airlines THAT message.
I suppose that this dry, real, message won't be well received in some quarters. Less wise and less experienced heads than many of the learned friends on PPRuNe may point to past glories, or note that they and their gran would definitely use a given service, or how many people in the pub tell them that Cardiff is too expensive to fly from, or perpetuate the myth that Cardiff is massively expensive to operate to. But sadly the message is the hard, cold facts of life in the airline industry today.
No amount of abuse of the airport management, abuse of the WG, or abuse of the messenger by the hard of thinking will alter the facts.
Cardiff is a huge risk for any operator, and in these times, no-one wants risk.
TA