Another 5 boxer buddy of mine has less than 500 spell damage and was able to do almost everything except the first boss. Do you have any clicky trinkets that you can use every 2 mins? Staggering out your thunderstorms will make trash very simple once you get the hang of shooting once or twice then bouncing them back.

On your opening dps target try shooting a lighning bolt first then followed by an immediate chain lightning they should both hit at around the same time.

Another 5 shaman boxer Nitro posted that he speced one of his toons as restro and had him target the main guy and spam chain heal. This might help if you are dying alot. Just keep trying you will get down the pulls and eventually the whole instance.