What type of content do you focus on? [PvE/PvP/Both]
Both.
If PvE, what type of PvE? [Heroics/Raids/Other]
All of the above. Main focus in PvE is raiding.
If PvP, what type of PvP? [Arenas, BGs, Rated BGs]
Arena. I would do RBGs if I could find groups though. I have not done Arena this season.
What are your biggest quality-of-life issues? For instance, no longer requiring ammo could be considered a quality-of-life improvement for hunters.
Attonemnt healing not reaching players due to a large hit box (Rangaros). Inner WIll/ Focus duration change was the biggest QoL change since removing the buff reagent via glyphing. We do not require anything, off the top of my head.
What makes playing your class more fun?
Fast-paced healing. Be it frantic Circle of Healing casting in Burning Crusade, to Renew covering as Holy and PW: Shield covering as Disc in Wrath or heavy reliance on Prayer of Healing in current content. While I think it's nice to have us choose the right spell at the right moment, it's clear that it cannot be balanced by 5 healing classes for this style of raiding. Therefore I think it's better to have the fast reaction "whack-a-mole" healing that Wrath of the Lich King displayed.
What makes playing your class less fun?
Over the other healing classes? From a mechanic point of view, nothing. I wouldn't mind playing any of the healing classes. What keeps me to my Priest is sentimental attachment and the stock of pets, mounts, achievements and titles.
How do you feel about your “rotation”? (Rotation is the accepted order in which abilities are used to maximum efficiency.)
I covered this two questions above, but to re-iterate, I think we need to make a move back to Wrath of the Lich King life and death healing. You went from saying mana would be an issue in beta to it becoming trivial during Tier 11. Regardless of nerfs to Innervate, Mana Tide Totem and increasing the cost of our healing spells.
What’s on your wish list for your class?
I wish Discipline would get a new Mastery. Divine Aegis is only good when there is constant pulsing damage or at least moments of flashing damage (see: Blood-Queen Lana'thel in ICC for the former and Twin Valkyr when they periodically cast their Vortex for short periods of pulsing damage). In a lot of cases, we heal up the raid after a big AoE hit and our Aegis is useless and falls off everyone but the tanks. Holy has a great Mastery, it doesn't force you to stack the Mastery stat (there's a choice between Haste and Mastery for players depending on their healing style, which is great). However, Holy has found itself benched in Firelands due to the lack of a proper raid cooldown. I know you do not consider this to be an issue, but why bring a Holy Priest when a Druid can match (and beat) it for raw throughput and then bring Tree of Life and Tranquilly to the table (and a combat res). It's not been the biggest issue since we have all been able to just spec Discipline, but it's a case of "forcing" some Priests to play a spec they'd rather not just so they can raid with their guild at a competitive level. Shadow is fun, it's my off-spec for Firelands and it's neat. Fair enough by moving the damage from DoTs to cast spells. Shadow is in a great place at the moment.
What spells do you use the least?
As Discpline: Renew, Holy Nova and Divine Hymn. As Holy: Guardian Spirit, Holy Nova and Divine Hymn. As Shadow: Nothing. All relevant damaging spells are used, even Shadow Word: Death pre-execute range.
Additional/ summarised thoughts:
I would like to see a change made to the Hymns given to Priests in Wrath of the Lich King. Divine Hymn has a long cooldown and requires the Priest to stand still for quite a long time. Hymn of Hope doesn't guarentee that much mana return to the actual caster of the spell and again, requires a lot of standing. Shadowfiend can be unreliable at times, is this intentional? Holy needs a raid cooldown. Discipline needs a new Mastery. You don't need to make Critical Strike an attractive stat for healing, we have Spirit / Haste and Mastery to look at on gear (and Intellect when gemming).