TCD DO NOT use the 150 points conversion though (I think all of the other unis do though). English and History TSM is extremly competitive, they're the most sought after individually. I myself got 500 points in my leaving cert and missed out on TSM History by 10 points, it never dropped at all. That was 2007 though.
If you don't have 4 A-Levels to present you are a hit-and-miss case and shouldn't expect anything, it's not on the same level as us who present 6 subjects without fail. I don't think you have a realistic chance, I think you might have a chance. If you get the points you are not in for sure! Lots of people overlook things such as matriculation requirements (foreign language Leaving Cert level/GCSE at least/no non traditional subjects are considered (as we don't have any of them so it'd be unfair) ag science may not be combined with any science subject etc you have to pass maths and so on.)