W124 axles were originally secured with 10mm XZN (aka 12-point, triple square) bolts. Yours might have been changed to Allen. My guess on why German car manufacturers use these are massive torque handling and the fact that Torx was patented until the early 90s.

As for beveled bit tips, that shouldn't make any difference. The percentage of bolt socket depth not engaged because of the bevel is insignificant. If you're camming the driver out of a Torx bolt, you either have a crummy Torx bit that's made to loose specs, crud in the bolt socket, or the bit isn't seated at the bottom of the bolt socket.

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RIP:
2011 E350 BlueTEC, Schwartz 81k (totaled by uninsured drunk driver)
1964 Unimog 404.1 (wrongfully towed by the city)
1994 E320, Brilliantsilber 208k (transmission shuffled off after sudden catastrophic fluid loss)
1982 300D, Silberblau under a blue repaint 256k (sold for parts)
1995 E320 Polarweiss, 131k (sold for parts)
1995 E300D Polarweiss, 287k (totaled by drunk driver)