This is why folks ask what your interests are.
You're wanting out-and-back day or half-day walks, yes? I'd say these are available all over Ireland. I looked up Rosslare, and it definitely has several options. I'd recommend you go there directly, then Tramore (why not just stay there instead of Waterford? It looks lovely), then Cork. Stay at least 2, preferably 3 in Cork, from which you can visit Cobh, Kinsale, Blarney if you want to do that. Then Skibereen. These are all pretty easily done by bus.
The thing to do is to prioritize the walks you most want to do, plot them on the map and determine the most convenient bases that give access to them. A base doesn't have to be a city you've heard of or that has a lot of tourist infrastructure. Unless you're wanting to combine your walks with traditional sightseeing.
What I like about your itinerary is that it takes you off the beaten track, to an extent, which probably gives you better odds of having some of these places to yourself, and isn't that the goal of a walking holiday? I expect you could take the east and southeast coasts at a slower pace and find a lot to occupy yourself without having to spend long days on a bus or train.
There are also several long-distance walking routes that you could do in whole or in part, as a through walk or a series of day trips.