I reject axiological hedonism. I don't think anything has intrinsic value or intrinsic disvalue. On my preferred view, all value is projected subjectively onto the world, and pleasure is just one way, among multiple, to find something "good". Conscious approval is another way to find something good, for example. Things are only (dis)valuable if they are (dis)valued. I describe this view in this piece, and some more implications here.
The disvalue of suffering is self-evident from introspection, i.e. from observing how suffering feels.
Could you elaborate? FWIW, I don't really think anything is self-evident, maybe other than direct logical deductions and applications of definitions.
The disvalue is inherent in the experience; it is not a matter of an evaluation done by me, or a desire for the suffering to stop felt by me (even though there is a strong correlation), or me having a certain attitude towards suffering.
I would say suffering actually is an evaluation done by you (disliking) and a desire (wanting). The evaluations and desires inherent to suffering are kind of hardwired in, not reason-based. They are not the kind where you decide by reasoning that something is bad and to be avoided. They are forced onto you. These are empirical claims for which I think there is some evidence from cognitive neuroscience. I discuss this more in this piece and this piece.
See the Theories of Well-being chapter at utilitarianism.net for a detailed philosophical overview of this topic.
The simple case against hedonism is just that it is bizarrely restrictive: many of us have non-hedonistic ultimate desires about our own lives that seem perfectly reasonable, so the burden is on the hedonist to establish that they know better than we do what is good for us, and - in particular - that our subjective feelings are the only things that could reasonably be taken to matter for our own sakes. That's an extremely (and I would say implausibly) restrictive claim.
When you say "what is good for us", could it be translated as "what we are attached to"? If you care about knowledge or relationships, you will experience (dis)satisfaction depending on what relevant events happen in your life, and you will be motivated to achieve goals related to these things, but this is a far cry from what intrinsic value means in my view.
In essence, when I say suffering is intrinsically bad, I don't mean that it is bad for anyone; I mean that it is bad period. The badness is an inherent feature of the experience.
So from my perspective, the non-hedonist is making an extraordinary and unfalsifiable claim when positing the existence of non-experiential goods.