@Absolutely_Not your Nurses do need to support you more with your PICC coverings, and skin sensitivities. You shouldn’t be getting blisters. My Nurses were very careful that I didnt get any pressure sores, reactions, rashes etc.
When I did get pressure sores they were very active in reducing the risk, and applying a special barrier ointment on the sore areas before applying the transparent plasters.
I did become sensitive to the same plasters you have been using. Not as bad as yours, but I got that they couldnt use the sterile wipes without my skin flaring up. The plasters had made my skin very sensitive.
So they changed the plasters to a sensitive skin brand. Sadly I have no idea what name it was under, but it made a huge difference. It was transparent, like the other one but had two sides that had a flesh coloured edging to it, about a cm deep. One Nurse did comment on them being £3 each. And that they only came in small numbers in small boxes. Hence why they were sometimes a little reluctant to use them, as they ran out of them very quickly, or worried they may run out of them soon.
I always had problems with both types, coming loose at the edges. Especially in the hot weather, and if I got too sweaty. So I always had to have a supply of tapes, plasters etc to stick them down until my next visit to the Hospital. A few times, if the actual main part that fits into our arm/vein became exposed, I went to the hospital to have it re done properly. As there was too much of an infection risk. But if it was just the edges I mainly used Elastoplast Plasters just to seal them up again.
Micropore was useless. Within hours it just peeled off. But that was during the heatwaves. And due to my skin being too sweaty. It may be better now it is cooler.
I also always used loose long sleeved garments day/night to reduce the chances of rubbing the plasters against other things. That helped to some degree, especially at night when I was wriggling around in bed.
@wibbles from March Starters has very sensitive skin, so I have copied her in to see if she has ideas for PICC coverings. Wibbles you are an expert on sensitive skin. Any ideas?
But do push your Nurses re the blisters. You could also ring the 24/7 helpline to make sure your concerns are logged. That may just make the Nurses try abit harder if they know you have spoken to other medical staff. Even highlight it to your Oncologist.
I know £3 per plaster is expensive, but compared to £600 per certain injections, its cheap.
Chemo is tough enough, without being in avoidable pain/discomfort.
Hoping you, and anyone else having skin sensitivities, get improvements soon. 
i