Listen, y'all. I have heard many an Irish band over many a year, and they all have this problem - they wanted to use guitar with their music so they would sound modern and American, but their music was never intended to be played with guitar. All too often it moves stepwise to the point where no chord harmonizes with a measure.

So they invented DADGAD and then they clung to a brutal rackety strum which sounds like a train. Band after band does the same thing. (They have now taken to calling the guitarist "the engine room.") After a while, it all sounds alike and it all sounds ugly. But since most people are impressed if they only play loudly enough and fast enough, they get away with it.

Basically, so-called Celtic bands have turned the guitar into a crude percussion instrument.

If you go to a session, 99% of the music will be played in G or D, so it can be nice to tune your lowest string to a D, but that ought to be enough.