As a mainly constructed player, I don't have strong feelings about the classes in arena, but even I can see that things are pretty fucked up in there. Like when I get bored and decide to do an arena (my avg is prolly like 5 wins these days), even I can tell when I get certain classes that there just isn't a lot of good choices for that class in arena.
When certain classes rely VERY heavily on rare and epic cards to succeed in constructed, the chance of getting a "constructed-like" deck in arena is vanishingly small. So you rely on the commons of that class, and there are quite a few classes with commons that are really bad. Not even just bad for arena, just bad in general.
All of that said, there have been LOTS of easy or at least straightforward solutions to arena problems over the years and they have all been ignored, so I don't expect any of this recent spat of complaining to have any better results. I personally don't see any issue with adjusting rarities of cards for various classes. Does it mean that some classes will have more rares/epics than others? So be it.
Maybe only do the rarity adjustments after the cards move into Wild. That would at least protect the value of packs while the packs are on sale, then once everything is in the realm of dust, just do some swapperoos on the rarities. If they are really concerned about the value of dust and the dust economy (which I am unconvinced of at the moment), then it should be possible to make rarity changes so that the total number of rares/commons/epics doesn't change but maybe the total number per class is shifted.
There has also been a long standing ideas about assigning "fake" rarities to the basic cards. Players would still get all the basic cards free so the rarities would only be affecting arena and it would decrease the chance of seeing some of those high impact cards in arena. That idea seems pretty easy to do and doesn't really change anything other than arena.