I think everyone would agree that all Resto/ele shamans and all holy paladins use a caster shield, simply because they are itemized for the respective classes. With cataclysm coming, resto and ele are going to have the more readily available staves and caster offhands that now provide the now worth while spirit. On the mean-hand, Holy paladins will be able to benefit from the offhands, but not the staves (seeing as Paladins cannot equip staves lol.) Both will still be able to use shields, but would only be superior in a PvP setting for the added armor and the special abilities for paladins. The problem may become that shields will be very hard to come by, and most players will still want them for the extra survivability they provide.
The ideal solution? Get rid of caster shields (and in a sense just removing shields from Shaman period), and increase the base survivability of shaman to compensate. Shaman have no real talents that prop up the use of shields to begin with, and no real lore to support the use of them either. They were honestly put in vanilla wow to try and equalize Paladins to Shaman.
Now, that seems like a lot of dev work to do for a whole lot of nothing. The real beauty comes with what that opens up with paladins. Give holy paladins tank shields. Add a deep holy talent that converts the stats on the tank shield into healing stats (like strength to int and stam to spirit.) This would allow a higher itemization of shields in raids(and could be a good stepping stone on possibly removing spell power plate all together.)
Please, tell me what you think!
**On a side-note, I currently do not have an active WoW account so I am unable to post on the official forums. If any of you out there think this might be a good idea, could you please post this on the official forums, I would really like to see this change happen.**
-Tempos of Shadowsong
-Stelsol of Balnazzar
Peace