If you are interested in dealing with the one shot you should join the Ground PvP Bootcamp classes. You will be amazed at what we can show you. Your damage will increase and your survivability will also increase.
Being on the receiving end of a one shot usually means you didn't start playing the sequences before the other person. OR you overplayed your sequences. It really becomes a dance. If you run too few resistance buffs/debuffs on your end you will feel the effect of the opponent's super buff. If you ran too many buffs/debuffs on your end, you might run out of buffs, before your opponent does, and you will notice the one shot returning.
If you are being focused fired by a team, you can expect a combined 1000 DPS without major buffs on the opponents. If you have 100% dodge you can cut that down to 500 DPS. With 40% resistance you can boil that down to 300 DPS. Your shields for most players have 0% resistance so that 500 DPS will take that off in about 0.6 seconds. Your hit points might be at 600 but the 300 DPS will take that out in 2 seconds. So that results to 2.6 seconds from full shields to death, just from a 5 person team's primary fire using 1 strike team. This should give you a new appreciation for the use of hard cover (boxes and walls).
Ground PvP is a fast game.
For Engineers: In PvP your Cover Shield is not Hard Cover. It is considered Soft Cover and is Hard Cover for your opponents. Your opponents can destroy your cover shield very quickly but you cannot destroy your own cover shield. Therefore they can hide behind your cover shield but you can only do so for a short period.
If you are concerned about how to deal with Super Buffs then our Bootcamp coaches can show you how to manage the issue. We will even cover how to defeat the dreaded Cryo Pulsewave in session 4.
Here is how the super buff is done: http://youtu.be/FtaXbMASX7s?hd=1
That setup was using a Blue (rare) MK XII pulsewave with [CritD]x2. Which is nothing special.