What does it mean for law (or a branch of law) to be a 'cohesive whole' in the first place? Does it mean more than that the law (or branch of law) is not internally inconsistent? That seems to me to be a spectacularly low bar. In order to be cohesive, does law (or a branch of law) need to be capable of being explained by reference to one overarching principle (in the case of equity, presumably unconscionability)? That seems to me to be an extremely high bar, which I would be surprised if any area of law was capable of meeting, unless the 'principle' was defined in hopelessly vague terms.
I don't know the answer (and it is far too much of an arid philosophical question to interest me much). However, I do think it would be worth exploring what is meant by 'cohesive' before you try to decide whether equity is a cohesive whole.