Sorry about not replying sooner Gordon. I was gone all weekend, and just now saw your question. I am hardly a buffalo expert - I have killed exactly two. I would note I have been shooting stuff for most of my 62 years both hunting and in the military. So though I am not a PH, I have pretty extensive experience in the terminal ballistics of a lot of different projectiles. My response to the "rant" was directed toward the implication that "premium bullets" weren't that important so long as one hit where it mattered. My opinion remains that what one hits a game animal with is also important, that it is a part of our ethical responsibility as a hunter, and that the right bullet represents a small relative investment in that hunt.
To your specific point, I find the TSX bullet (not the old X bullet) worked perfectly on those animals and has given similar service to a number of friends and colleagues. Some of those people are in your specific line of work. However, I do not insist it is the only "best" bullet for that or any other particular animal. My rifle likes them and I have confidence with them. This summer, my son, of whom I am a tad protective, will be shooting North Forks - another outstanding premium soft. My .318 WR loves the old Kynoch 250 gr soft, my .404 does best with Bear Claws, and I again use the TSX in the 500-450 barrels of my S2. This summer, I'll shoot TSX'x in the .375 barrels and North Forks in the 30-06. But to be clear, if a rifle likes them the TSX is my first choice .375 and above.
I am really surprised by the petals breaking off the TSX bullet - I assume these were 350's from a .416? This was a common problem with the old X bullet - they almost always shed one or more petals. I have probably recovered a dozen TSXs in different calibers over the last several years and as I say, have a large circle of friends who have looked at many more, and none have done this. Not all were shot at cape buff, but a lot were (and eland, water buffalo, and the like). Are you certain these are TSX and not X bullets? I am holding one in my hand which drilled through both shoulders of buffalo (lodged under far hide). Like all recovered TSX bullets the grooves are very pronounced. (Will try to post a picture shortly). Expansion like every TSX I have seen was perfect. I do not see those pronounced grooves in your bullets. Had you simply posted them, I would have identified them as the old X bullet doing exactly what it always did when hitting bone.