Maybe Mercedes should focus of the reliability of their transmissions vs focusing on competitors. I will never buy another Mercedes - ever.
Guess what? It's not just Mercedes. I don't know where Mercedes gets their transmissions, but the automatics (tiptronic or not - actually, in some cars, it's a software and shifter issue only) that VAG gets from ZF seem to be quite crap. The A8Q I'm working on right now is on its second transmission, and the first one was replaced in about year two. As leaky as this car is, I wouldn't likely have bought it if it had been on the original slush box.
Germany was the watchword for quality up until the late eighties. But German cars are now, I am quite sorry to say, shit. My father once explained to me (repeating something a wise man must have said to him) that the Germans believed in using the best parts and the Japanese believed in doing the best design such that you could get away with the cheap parts. My experience is that these are in fact the design strategies employed by these nations. The problem with the German strategy today is that the companies making their parts are now making shit. Bosch is now turning out at least as many total turds as roses, for example, if not far more, and all of these German cars have Bosch ignition and traction control (etc.) systems — all the VAGs, all the Mercedes, and all the BMWs, as far as I can tell. These are both exquisitely expensive and poorly designed, vulnerable to water intrusion and for some reason these days typically mounted in the engine compartment. Except my LHD D2 A8, which puts the ABS control module in a really annoying place up under the dash instead of upside down in the E-box right under the PCM where they put it on the RHD vehicles, even more annoying.
Meanwhile, there are very few things that were annoying back in the W123, W126 Mercedes days in the 1980s. Turbo oil return on the diesel was crap. The engine mounts are a bit overcontrived to the point that you can't really torque all the bolts without a special tool, or taking off a bunch of stuff.
PS: You would think having purchased 4 vehicles from Mercedes and plans for another, that would mean something. But you would be wrong. Their side of the story - we were late for our Series A service - hence tough luck.
It's the economy, brother.