there are 3 things that you can do to improve your survival in the vashj fight.
1, only use your fade if it is 100% necessary. That will save your fade cooldown. If you are using xperl and omen it should flash red when you are targeted. You should always be aware of where the nearest tank is when the elietes are about to spawn. if it is coming from the area you are near go give hyrion or heart, or whoever is tanking a big hug if you think it might be chasing you.
2. Always be aware of where the strider is. When the strider is about to pop try to figure out where its coming from. if you see it
stay away from it. When its being kitied, move a little bit closer to the middle ( just watch out for the eliets) and throw your dots on it if you have time while healing. That is the most difficult thing is to be aware of the strider, and move away if necessary.
I realize its not the easiest thing. but being pre-emtive about when the striders and naga are coming, and lookiing out for them is the best way to avoid them. I realize you have to heal while doing this, so its a lot to do, but with practice, and knowledge of how to go about avoiding them, you will get it
There is more to life than pew pew you know, like staying out of the fire so you can live to pew pew another day