If your getting sheeped as a 5 boxer your slacking on using grounding totems (they abosorb sheep and most direct magic attacks)

The nexus fight is one of manny complex boxing fights but usualy i just hit follow and turn eveyone the same way by moving around.

For pvp i would also recomend specing improved range on earth bind totem and put the totem on round robin.. Voila you got a frost nova with long range but shorter freeze time. (If you specced the earth,fire,water talent in elemental) <-- not 100% sure if its the right talent name.

Dropping 5 fire nova totems or 1 TOW and 4 fire nova totems also buy you some time in pvp.

A killer combo vs meele is to either drop 5 magma totems and chain heal or to drop fire nova totem,shock the target and blow of 5 thundestorms. Watch out for spell imunities like rogues cloack of shadow and dk's anti magic shield.. 90% pops theese after 2 seconds so just be patient and wait them out. Then blow them apart!!