Hmmmm hard question ... I am still not sure about the answer ...
I have 6.7k pretty much BiS War with Mourne
Full Warthful 6.2kish Ret Pally with Bauble that I play with high Resi 1200ish
And a fun thrash gear UH / Frost DK - but I have played Blood with Relentless+Wrahtful on Blackrock
My conclusions so far:
1) War is definitely TONs of fun for ME cause I like a lot of mobility - charing around fights from person to person is something I really enjoy :D what I don't enjoy much though is when your teamates don't heal you - BUT enemies get healed :D that sucks ... but I have also won many 1v3s and more - aginst lower skilled / geared people in BGs - especially past week
2) Pally is by far super good playing solo - especially if enemy has no healer - also I like to play my Pally more defensive helping people around me and healing them too and cleansing and stuff - but not too much - especially if we have other healers on our own - is really about striking that balance between doing enough DPS to be effective and yet still throw that cluth BoP on Mage or Sacrifice or Flash on War when needed :)
3) DK I can't say much about UH or Frost cause I only played those in Thrash Gear. But on my Blood 50k-60k ish HP 1300 Resi DeathGrip Bot I had ton of fun taknking front lines grabing ppl to their death with super low CD :D
http://armory.warmane.com/character/...ckrock/profile
Is more of a Survival BG Spec - feel free to try it on BlackRock :D is also super effective for duelz :D
Duels lost 65
Duels won 96
So to make some conclusion - I would buy Shadowmourne / better gear on char you like the playstyle of the most ...
My choice with War was cause he is Gnome and I don't like to have the responsibility to buff and heal people - hence I chose a class I only press 1 button to buff - Battle/Commanding Shout - and I don't have to heal.
Maybe if I knew better how DK works I might considered that class, but I don't like DK spell animations - except Frost those are cool :D
I do like Paladins animations a lot and I am considering getting Shadowmourne on my Pally, but I am just not sure is worth / needed since I am already toping killing blows charts in BGs on my Pally as much or even more then on my War
And THAT MIGHT be the LAST THING to consider!!
If you only gonna donate for FEW items - meaning your char will be about 6kish GS for PvP I would pick Ret over War ANY DAY! I think Ret in 6k GS >>>> War in 6k GS as far as fun in BGs and even Arenas go. Same for UH DK.
Basically on lower gear (6k) DK+Ret are WAY better then War. When BiS I like War more though :D