By now, Ireland has a higher GDP per capita than the UK, and has had it for last couple of decades.

I’m not sure being a tax haven for multinationals by giving them sweetheart deals when the intentional loopholes don’t suffice is really indicative of a robust economy.

As long as it serves the local population (and apparently it does), I don't see why it's a wrong thing to. Ireland is not just a paper-holding tax haven; it has huge factories and engineering offices of large and successful corporations, again, employing local folks. I don't see how it might make its economy frail.