What I've personally always liked about WoW PvP was that it provided such a huge skill cap you could literally 1v10 at some point in time.
As I've played quite a few MOBAs over the years as well I think an appropriate comparison would be DotA/DotA 2 with HotS.
HotS is kind of a nice game and I've played it quite a bit but, honestly, everything is so streamlined - damage numbers are pretty low and can't fluctuate either because of the lack of items, personal level, and all. It definitely has polish because it's Blizzard we're talking about here after all but you can't really shine. If you're experienced in the genre and have brains it wouldn't take you any more than a couple of days to become above-average. And even then you can rarely 1vX as, like I said - everything is so streamlined and "team-based" that it would just not allow for that.
DotA on the other hand... the sheer number of characters, items, mechanics (even the ability to chop down trees is a very nice touch) made the skill cap so high that you could pretty much always improve. And when you did good you could even solo a whole team and it would feel so rewarding.
It seems like WoW PvP felt a lot more like DotA in the past and nowadays it's just another HotS.
The second thing - the reason I would've actually preferred it over a MOBA any day of the week - was the sheer amount of buttons I could press. In your regular MOBA you would have 3 spells on 6-10 sec cooldown each, an ultimate ability on a 90 sec cooldown, and a few items/talents/whatever you call it, often times on even larger than a 90 sec cooldown. In your regular FPS you would have a lot of weapons to choose from but at the end of the day it would still come down to two buttons, a knife, and possibly a grenade too. Playing WoW often times felt like playing the keyboard. That's probably the single game that has taken the full potential out of keyboards over the last 13 or so years.
And for some weird reasons the current designers in the WoW team are striving to shift as much away from those two things as possible. It's sad.