Lockdown hates me :<

What evil force or secret is keeping enemy guardian shields up after a barrage from several people, yet mine going down in two slashes from a single unheated 2* snarble barb? And why do all the other strikers have 20 foot long swords? Why do my swords fail at killing an unshielded weak armored person in 3 whole audibly connecting barrages and they can dispatch me in one or two hits?
Either Krogmo is booby trapping my equipment or the PvP gods hate me.
/pointless rage topic, move along

three possible answers
1) the other's weapons are not as powerful. For example, one guardian can hold out a long time against several gunners.
2) Your opponent has full inspect off and it's really a level 10 weapon
3) Your opponent has good trinkets and UV's.

Reason is pretty obvious though most people don't recognize it. There is a period of invulnerability after a player gets hit, whether shielded or not. The guardian you and your teammates were wailing on basically benefited from that invulnerability and was able to take a ton more hits because a lot of them wiffed and did nothing.
Unshielded doesn't mean low health, recons have almost as much health as guardian and a lot more than strikers. Also it is impossible for you to deal damage with all 3 hits in a 3 hit combo because of the invulnerability mentioned above. The second hit just doesn't register.

Nodocchi is right
To test this out get a cutter and attack a switch in IMF or somewhere. The switch wont change for every swing you do.

Was about to remark the same thing as Nodocchi.
This is why it's dangerous to use haze bombs on guardian packs, in the best scenario you're forcing them to shield going *plinkplinkplink...* and being generally invulnerable but taking them out of the fight or decreasing their shield a tiny bit.
In the worst case they're skolvers (immune to a shivermist, the most common bomb) who shield anyway to set up a trap, then when there's several strikers/recons trying to hit them from behind they suddenly drop the shield, turn around and Gran Faust/Divine Avenger combo everyone for a triple kill.
Argent peacemakers, Sentenza's, Cutter line swords, a lot of fast-hitting weapons have prevented my Gran Faust from connecting when it would have destroyed the guardian in question if it had hit.
In any case, you could receive some hints if you'd list your gear and in what country you live. In general anywhere but the USA will give you a latency disadvantage against American players.

I'm using a Tempered Calibur and a Magnus, tier 2 PvP. I want to prevent myself from just whining, but what can I do to work around lousy team mates? I don't want to sound Chris-like and be all "I'm so much better than them" but often I'm on a team that can't focus or work together. A lot of players i get grouped with dash out on their own, charging straight into a battle they clearly can't win. I can accept when I lose, even in the 'glitches' or 'lag' i encounter (that is apparently game mechanics I don't know how to work with), but killing someone by means other than being carried by a bunch of pros would be nice.

You can try to give some vital info to teammates, like "point 2 contested" or give general tips like "I need 2 guardians and a few strikers in a pack, the rest scatter" to loosely follow effective strategy like that detailed in Zetta's strategy guide. I've had teams form up after someone took charge and make a comeback.
You could take some other gear with you, Magnus is decent for gunners but gunners rarely stay on a point (which makes them deadly given enough time, but not so good at capping and therefore winning). Calibur is in general not that great of a pvp weapon. Go get a sealed sword and just level it to 10. Its big arc gives you a chance to hit multiple people, which is one way to even odds.
You're not the only one.