I feel WHM is the easiest healer to play, and in SHB it was impossible to raid as a WHM because they were literally everywhere. Even now I see a bunch of WHMs in PF... so I do feel the other more complicated healers should be marginally better and they are. Looking around this has barely dented their popularity and if you search for statistics online it does seem any places with info about it support the fact that WHMs are still as popular as ever.

It is likely SE made them ever slightly harder to play and just a bit underpowered to encourage people to use other healers. It's just my guess.

I only have WHM leveled and geared at the moment, and you bet it was because it's the easiest most straight forward healer. Plus the Aesthetics are nice. So viewed through that lens I'm not really upset about it's state because I put a lot less work into playing WHM than any of the other healers do to play somewhat optimally.

TLDR its not great, it's just okay.