He's right. I've been able to do it, and I'm not even the best at it. Tacs with Fire Team or those dirty gankers with an Operative kit can do it, no problem. Combine that with a large power cell and you got a seriously big stick to hit someone with.
You want to counter them? Sci officers with the proper healing kits can take any abuse these one shotters can handle (I know... lousy healtanks need to be nerfed). Or if you're an engineer, a timely weapons malfunction/hold/orbital strike works wonders (lousy weapon malfunction needs to be nerfed...). Or if you're a tac... either try to outsniper them or go the coward's way and use your Ops kit.
Polyalloy Weave or Energy Dampening armor is a must. if you know your enemy's weapon of choice get armor and shields with that particular immunity (if the guy's sporting that retro Type III then it should be an easy call to make). MACO's great for the rechargable shield. Don't discount Omega Force set either... it does wonders for your crit severity!
And hell... you should be sporting a pulsewave and retro rifle combo yourself. There's a reason why they're popular. They're effective! Don't want to be part of the herd? Then use the classic Sniper Rifle... it's a lot slower to use its secondary fire, but it does have superior range. There's also compression pistols, which work similar to pulsewave weaponry. I've seen some really good grounders with compression pistols just waste people (and its secondary fire cooldown is faster!).
Something overlooked, however, is weapon bonuses. One of the reasons why these one shotters work so well is because they're sporting weapons with insane bonuses. I myself sport a Mk XII pulsewave rifle with a 60% at crit severity (CritHx3 I think, correct me if I'm wrong). When you've been exposed, how are you supposed to reasonably get up from that? Still, I wonder if a better crit chance or better damage would be more effective...
Mind you, I haven't revamped my grounder in awhile and I'm not the best (but I am fairly good), so take what i say with a grain of salt. Still, it should help.
Use the Retro Klingon Pistol... I can utterly DESTROY people with that wicked thing. Knock Back + the highest DPS of any gun in the game. Now if you can sneak up on someone with the CRM full charge lol... Say goodbye.
However, to be honest ground PvP is an utter JOKE... Space PvP has some major flaws but ground is about 10* worse.
No tactics, buffs/debuffs or gear should allow you to one-shot another player.
Granted if you practice and invest in the right gear and skills etc you should be able to dispose of your enemies as quickly as possible. But a fight should be a two way street and the game mechanics should allow an opportunity for a player to respond to an attack.
I think one solution is no weapon should be able to strip half your shields with one shot let alone one-shot kill you. So an initial attack only has the potential to remove at max half your shields on very rare large crit hits.
Don't get me wrong there is a certain amount of satisfaction with killing your enemies within a few shots, but it is not fair and it should be a much more balanced dog fight. (This is based on two opponents having roughly the same gear)...
Two opponents with MK X gear for example, one with common and the other with very rare; the very rare geared player, whilst they will have the clear advantage, the common geared player must have the opportunity to first defend and then retreat if they can and decide to. The very rare geared player should not be able to one-shot them, but with the clear advantage in regards to gear and with equal tactics, they should most likely win the battle. Although common geared player should have a chance to win depending on tactics and skills etc.
It is a complex thing to balance, but bottom line is no combination of tactics, weapons, gear and abilities should allow a player to one-shot kill another player.