I also can't comment on other specs since this is the only one I've raided with significantly (and I've only raided at all with this one and a monk)
And despite the title, I actually do like playing my holy paladin, but after running a few raids with her this xpac I've run into what I consider a problem:
I don't feel I have enough tools to do what Blizzard expects healers to be doing in this expansion.
What do I mean? I mean that a big point of healing right now is that your Mana efficiency matters. You'll go OOM eventually, faster if you spam, so you need to carefully manage your mana in order to keep yourself going for the entire fight, especially on long raid bosses.
The problem I have here as a paladin is that I can't really do that.
I have four mana using heals, two that are fairly efficient, two that are inefficient. Then I have an AoE heal and two manaless heals, one AoE and one single target.
The problem here is that my most efficient healing rotation is also my primary rotation for all situations. The inefficient heals? One of them I cast maybe once a raid (not once an attempt, once a raid) at best, the other one only in extreme emergencies, and even then very rarely.
As for mana regen itself. I have two options, a long cast time (when glyphed) spell that gives me a small amount of mana on a several minute cooldown, and an instant heal that restores mana on a very long cooldown.
What I've found out this means is that I don't really have any options to be "more" efficient. My mana regen tools are on a long enough cooldown as to not be a serious lifestyle change to rely on, and I'm already casting my most efficient spells simply as par for the course.
What this seems to amount to for me is that my only real option when I want to be more mana efficient or regain some mana is to just not press buttons.
I realize to a large extent this is unavoidable, but the simple amount of time I actually spend right now not trying to heal people feels wrong to me. Don't know if anyone else feels at all similar here though.