I find that it mainly boils down to pubs having more, quality premades than imps, and the queue system benefits groups of 4. So make some friends, hop in some voice comms and roll some pub!
I would have to agree with Mr. Vasyel here.
I thought Imps pvped like the scum of the earth, but what it came down to was that I was primarily solo q'ing. Been using "Imppvp" chat to form/join premades which has increased my winning by quite a bit. Even if we don't get into voice chat together, I can count on at least half my team being competent
"simply walked behind a vanguard, said, "Hey, don't notice me" and proceeded to cap while the confused vanguard ran around."
Edit: Add me as a friend and shoot me a whisper if you want to pvp. I'm always up for a few matches so let me know. I am working this week though, but I will be on next week for the most part.