With principia simulating vessel rotation during time warp landing autopilot is almost useless.
At the moment autopilot will try to freeze vessel's rotation by engaging time warp, this doesn't work with principia, and leads to constant reorienting-warping loop that burns all RCS fuel.
Either
a:) change the behaviour to warp to 30s-1minute before next manoeuvre, then orient vessel and fire engines.
(now it's orient-warp-fire)
b) orient vessel, wait 10-15s to kill all rotation, warp, readjust, fire. that's how "execute principia node" seems to be working now, and is pretty efficient.