Let me start by saying that the title comes with built-in sarcasm. The text below does not.

I'm not making accusations, or starting some crazy Mech Arena conspiracy theory, but why does my game lag during 5v5 matches whenever human opponents are involved? 

Because whenever it's just me and nine Bots, my Juggernaut maneuvers the terrain like a buff IG series assassin droid hopped up on JP8 fuel, weaving gracefully around my AI teammates and landing shots with deadly precision. And every gameplay, win or lose (yeah, I lose to Bots. It happens.), runs smoothly. No lags. No glitches. 

It's a different story whenever there's one or two humans in the opposing team. My mech constantly freezes up at exactly the wrong moments - when I've got an opponent lined up in my sights, when I'm about to activate the mech's ability, or when I need to dodge incoming shots.

This convinced me that I'm only good at the game when fighting Bots, leading me to decline countless invitations to join a clan. Because who wants to be that guy who brings dishonor to his clan?

(I have recently joined a clan because the player who invited me was nicely persistent about it, but so far has been a very passive member).