Against assassins you need to use some tricks for easier fight. For example with time you learn you can easily avoid Lightning Sentry just by walking around (instead of teleporting). If you teleport all the time, there is higher chance LS will hit you from the edge of the screen. But if you perform a short walk, all sentries will completely miss you.
Other more advanced and better trick is Weapon Switch trick or Weapon Switch Glitch as some call it.
Here is video of some guy demonstrating what that is and how it works:
How it works: you switch weapons fast and walk. Every time you switched weapons, hit recovery is reset. This means assassin will have much much harder time to stunlock you since you will be able to move. But you must WALK for it to work. I do that too when some assassin namelocks me and spams traps and mindblast. Just WSG out in a fine curve and you won't get stunlocked and with practice you will avoid all the damage as well (LS hits in straight line, so if you walk in slight curve, they will all miss you). Against WoF you just have to walk and it won't even start firing since check range of WoF is only 10 yards, and you have enough time to walk out of it before it starts shooting. Even if it starts shooting, you will be far enough to avoid damage from it.
If you don't try nor perform WSG, you will get stunlocked much more frequent. In fact, without it if you find yourself in trap field, it is gg. If you do WSG, then you can escape with limited damage taken, depending on situation. Sometimes trappers have hard time doing ANY damage if someone wsg-s out. Sometimes I got namelocked for almost 10 seconds by a trapper because it was dead end, and I wsg-ed my way out with taking maybe only 1-2 LS hits in the process. Without it would be gg pretty much.
Walking is very important technique against assassins to prevent stunlock. New players try to teleport out and that won't work. Why is teleport not working and walking is? Answer is in deeper mechanic I will try to explain. Every action in diablo has its action frame as well as execution frame. Casting frames are actually execution frames, when you do the complete casting of some spell, including actually casting the spell and backswing animation. For example 105 FCR sorc has what all know 8 frames cast rate. Those 8 frames are divided like this: action frame is 5 which means it takes only 5 frames for sorc to cast a spell, while last 3 frames are only backswing animation. That is total of 8 frames.
Apart from action frames, there are also hit recovery frames. All know what those are. 86 FHR sorc has 7 frames hit recover. This means when she is put to hit recovery, she is helpless for 7 frames. If we assume same sorc has 105 FCR aka 8 frames casting rate and 5 frames action frame, that means sorc which is put to hit recovery needs opening of 12 frames (7 for hit recovery and 5 for casting spell) to escape from stunlock.
If assassin is mindblasting you + traps are hitting you, it is fairly hard to find such window to escape with teleport. That's why player who tries to escape only with teleport is likely to get stunlocked to death.
Walking is different. It has 0 action frame. This means after 7 frames of hit recovery are up, sorc can walk any direction she wants. She can try to walk out of traps and will have easier time than trying to teleport. Also walking makes traps miss you since you are constantly moving. While you teleport, trap has higher chance of hitting you. Naturally, walking alone is not enough to get out of stunlock. But in combination of WSG and walking, assassins lose A LOT of stunlock potential. Actually it is nearly impossible to stunlock experienced player who learned to do such trick.
In a way, PvP is a "science" with big learning curve. Also yes, ES sorcs are in big disadvantage against trappers, but they can help themselves with wsg trick. Vita sorcs have easier time since they don't depend on ES which is slaughtered by few trap shots.