I know for a fact that several centurions in Crushbone and Greater Faydark will con as an even fight at a lvl 4 character. Keep in mind that, at least in CB, the orc centurion's level ranges get much higher the closer you to get the castle.
I find that area there in decides the level that they are,in East Commons they run about lvl 9 to 10 as a even fight and the ones outside of Kelethin as low as lvl 5 or 6.
The Cents just out side of Kelethin on Orc hill (We call it that on Tallon)Are farely weak some shamans are lv 4,Oracles are very ranging in lvs,Cents can even be lv 4 and I think at lv 4 I saw one that coned blue!And belive it or not there are pawns on the hill also.
CB Orc Cents go from lvl 4-9 in CB (I have yet to con a white or higher with my lvl 10 ranger) Lesser Fay Orcs are lvl 4(rare)-11 ButcherBlock CB Orcs were all red at lvl 9 GFay orc cents lvl 4-9