Sadly, I don't think that the low rate of Carers Allowance in itself could be considered in breach of human rights, because in the vast majority of cases, it is only one component of the household income. In fact, anyone who is living on CA and has absolutely no other source of household income is also almost certainly entitled to other benefits such as housing benefit and so on. I have no idea how many people fall into that category. Certainly many, possibly a majority of Carers eligible for CA also work part time, or have spouses who work. So, no collective breach as such because each case is different. As for absolute poverty and human rights, there are many parts of the world where the average household income is less than £600 per month, and billions are below this line, so it's all relative.
This is not to say that I don't agree that CA is far too low, and I would personally argue that it should continue past retirement age and be paid to full time students, and that the earnings threshold should be tapered so that everyone has an incentive to get a job if they can.