Even a green geared paladin with minimal spell damage gear should be able to keep aggro from green geared elemental shamans.

Make sure you have retribution aura, sanctuary blessing, and rightousfury up, and just wait like 3 seconds before u start nuking

Never let Holy shield down as its great aggro.

I really think once u get that working, u can do SL for instance very easyly.

Anyways as to your problem, i am fairly sure you skipped a WHOLE lot of quests. Either u go back and do some of them or u keep at trying to run instances.