Regarding pure IK+BK I have been able to do grift 43 without unity (RoRG + hexing pants + skull grasp) and with only one ancient BK weapon.
Actually I play with CoE ring + skull grasp and two ancient BK weapons, I can reach grift 45 eisley, don't tried to go higher atm.
Rifts up to 40 just melts, I do test run just a while ago on grift 40 - 10 min left with this setup.
I also try to go WotW + 2 + 2 setup because I really hate IK weapon, and I need to admit, that without berserk it performs very well, considering survivability - better than IK + BK.
I know (by scoreboard performance), that 6 WotW + 4 IK > all other builds, but I don't like to play the game in the one and only way that devs consider the best.