IT’s looking like I’m going to have to level another priest to level cap.
I love playing shadow. I have played shadow since WOTLK and its always been my main. I am also starting to get into disc, not just for dungeon healing to get my Northrend Supply bags but also because Disc is very good in PVP right now especially Arenas.
The problem is that duel spec only always two specs. For instance Shadow has basically the same tree in pvp/pve besides the points you spend on Silence/Pyschic Horror. Disc is similar but with many more varieties you can go with.
My point being that in order to get the most of this game, content and spec choices for my class I need at least 4 minimum spec loadouts (Shadow pvp/pve and Disc pvp/pve) and thankfully I have no desire to heal as holy in raids because that would be 5.
So you know where this post is getting at in the fact there is only a dual spec for WOTLK and I need at least 4.
Personally I think the idea of spending 50g every time I want to go pvp as shadow and then 50g to change it back to raid with my guild then 50g again to go pvp some more an unnecessary game mechanic that adds nothing to the game other then me vendoring 50g to an NPC that just disappears into thin air and never contributes to the game again in any way.
I don’t see why a player cannot have as many spec sets as he wants for whatever situation he wants on any given class when that only would positively impact his ease of access to play the game and would have zero negative repercussions (because everyone would be able to do the same) You can’t change your spec mid combat so that would not allow players to abuse specific specs for a specific player/class/spec.
The only people I could see having a problem with this are those who simply have the attitude of watching the world burn. What I mean by that is I already foresee certain players with 1 class that has 2 cookie cutter specs and nothing else to come in here and tell me that “two specs are enough” (because it is for him) and does not wish to see anyone be able to play their class to their full potential, thus giving them the advantage. Or just those types that don’t want blizzard to give anyone anything innovative because “wow classic hard, go play retail if you don’t like it” or quiet simply the unhinged trolls who would rather lick boots and do as they are told and will say “stop complaining/whining/using your words” rather then see anyone create a positive change for the community.
That being said if anyone does have a logical and insightful reason as to why a toon should have to pay 50g every single time just to respec a few talent points depending if they feel like PVPing or PVEing that particular day/hour/bg/arena.
IF you read this all and made it to the end congrats, here us your uwu cookie. 
EDIT
Here is an even better example. I raid every weak so my 1st spec is shadow PVE. My 2nd spec is Disc PVP so I can Arena.
I neede to farm fire eternals for so I can make titansteel bars and Sapphire spellthreads.
So there I am in WG fighting a DK for mob pulls who is beating me 2 times out of 3 just barely while we are both in pvp gear. The diff is he has AMS and Army of the dead and silence. I don’ thave improved fear, silence, or disarm because my spec is set to shadow PVE.
So now I have to go to SW and drop 50 gold to respec to shadow pvp, go back to the spot to farm, see if he is even still there to fight and then when I raid that night I have to pay another 50 gold to switch back to Shadow PVE again or else lose a bunch of DPS and disappoint my raid.
The only experience I am getting from this mechanic is the experience of being punished with gold for every time I want to play the game in a different way, thus enjoying the content.