Five years ago, the price of €1100 would to me be good low price for a 3 piece, esp if a full three seater. Did the shop offer you a warranty on the leather.
I know houses who paid €3500ish for a suite and I paid more than that for a cream leather corner unit and all leather was showing usual wear and tear ie cracks/smoothness or baldness where areas of most use after four years old (cost €4200, designer make and sold it on for €600).
There is a certain amount of maintenance required with leather. I know I used expensive leather care kit that I purchased from the original furniture shop to keep it from cracking as they said to let the real leather dry out would make it inflexible and so break/tear under the weight of a person (after the first kit gone I used stuff from car shop, this was €20 a bottle and took a half a day to put onto and rub off bringing any dirt with it).
Which is why i buy fabric now, Have a suite all cushions/armrests removable and machine washable, six years old and as good as new only style a bit dated.
I do appreciate your disappointment but I feel your at the mercy of the goodwill of the shop.
PS check out donedeals.ie, adverts.ie as extremely good value can be had there, especially as your rental properties.