Outside the arena you can buy a spell to reduce critical for 0 pips, I've blocked every critical attack when casted. You can buy it for one training point and guess what? It got a 90% stun block too. Just a thought
That has happened to me but I just dusted myself off and went at it again. Criticals are random and it's not storm wizard's fault that they have such high criticals percentage. Maybe you need to train conviction or even storm shields. Check your gear also and your critical block...look at what you did/didn't do...also it won't happen again so just keep smiling and pvping