I expect you are correct in assuming the XTP bullets blew up (without reaching vital organs). I think they are probably designed for maximum velocities of maybe 1400 fps at impact.
The Kieth style bullets, in 44 caliber, are fine at the velocities you are driving them, IF MEPLAT SIZE IS AROUND .300, and will completely penetrate deer from most any angle with a nice sized wound. If much smaller killing punch is not as good, and most so called Kieth bullets have smaller meplats. Please understand clearly I'm making this reccomendation based on your high velocities, with are above normal for 44 magnum revolvers. No 44 caliber bullet I'm aware of will kill as quick clean and consistently as the LBT WFN series, in weights from 260 to 300 gr., with starting velocities from 1200 to 1450 fps. This with NO EXPANSION.
I don't believe the Ox Yoke scoring tool will do a bit of good with hard cast bullets, but in fact will be detrimental, because if it induces expansion, fragmentation and lopsided bullets which do not penetrate true will be the result. I'm sure it will work very well to help pure lead muzzleloading bullets expand, which is what it is designed for.