Speaking from my experience, 2 years ago a landlord would nearly be insulted if you asked to lower the rents. The case today is different, very different, there are about 3 times as many apartments/houses for rent out there now and not nearly as many people willing to rent. landlords have bigger mortgages on empty apartments and they are scared about not getting someone to rent (especially reliable people). Look at daft.ie and take any popular, nice area of dublin and you will see that some apartments have been up there for months. I've seen apartments drop in rent anywhere from 10% to 20%. Who wants to rent a 2 bed or 2000+ a month, it's crazy to think there are many people willing to take up these offers. i've talked also with some agents trying to rent for landlords and they have spoken about how resistant landlords are in dropping rents, to there own detriment, leaving apartments empty for up to 6 months before eventually getting someone and not before having to eventually drop the price.
Once the banks come knocking at the landlords door you will start to see prices come down, not sure when this will happen but I'm guessing sooner rather than later. A smarter landlord will be open to offers and if trends continue ( [broken link removed] ) then the rental market will see prices come down sharply.