Generally speaking I find Dublin to be a very hard place to approach women.
Most women here socialise in large groups and their bitch shields are usually very high. The quality of Irish women in general isn't great either in my opinion, especially compared to the rest of Europe. Put your average Irish girl next to your average Slovak girl, for example, and you'll immediately see the difference.
I also find that they tend to go for the most attractive and extrovert men, even if they aren't great looking or all that out going themselves. So overall, getting laid here is pretty damn hard and probably not even worth the chase in most cases. I usually only approach foreign girls on a night out because they usually aren't as paranoid as the locals and usually more interesting and easier to talk to......but more importantly they are FAR easier to get into bed