Poison chars are usually banned in gm. Like plague, rabies and yes nova.
But a bone nec casting lower res in Tpk would b gm. Say if your partner as sin is alive

Thanks
yeah there was a poison nova nec on d2ga arena game..... that was casting LR.

Best thing u can do vs psn nec is have life rep. If he gets you to 1 life, fire golem usually will take you out with the fire pulse dmg similar to auradin. If your life keeps going up enough, you'll take novas all day and won't die. A good nec might use teeth too which would make it a bit harder. Also you can stomp on nova as it's being casted and it won't hit you.

Thanks for heads up.