If /ignore prevents players on that list from being in your group, then you'd want to ignore all the bad players, not the good ones. That way you aren't grouped with the baddies, and have a higher probability of playing against them.
I get that, but will never work as it's exploitable (to a degree of bettering ones chances anyways), thus why we don't have that function in PvP. Not to mention this game doesn't have the player base support to even make this work, even if it were implemented. This is why match-making is a failure in TOR, not enough players to make it work, cause EA ran off millions of players.
But yeah, I get what the OP is saying and don't blame him, but that's sadly part of the PvP experience.