im actually a huge fan of a full 40 into resto at that level. if youre going to twink, youll have a lot of stam and hp, and if you have a lot of hp, then natures guardian heals for a lot. i dont know how many times ive tanked 3-4 guys in warsong just by spamming LHW on myself while natures guardian procs every few seconds whenever some pet hits me for 50. meanwhile, my friends are off capping the flag or decimating the guys who are so desperately trying to take me down.
for reference, heres my shammys armory profile:
http://armory.worldofwarcraft.com/character-sheet.xml?r=Anetheron&n=Alyxsta
shes not as twinked as she could be, but shes pretty decked out regardless. i went for more of a balanced approach with my balancing of +healing and +dmg because i like the idea of actually being able to hold my own should the need arise.
the classes that give me the most trouble tend to warlocks and priests, due to fear, silence/spell lock, and dots. really twinked nukers can give me a lot of trouble too, since theres not much i can do if an elemental shammy CL crits me for over 2k. but for the most part i can hold my own and either win or last long enough for help to arrive.