I did a bit more reading and find the original 113 was gas. I s’pose I should have read that to begin with. We did have the A1 version, the only tracked vehicle we did have that was Gas was the very noisy M-88 retriever which needed the extra H.P.- Kw-PS given by the gas engine. Present day 88’s are Diesel I believe. Navigating in the 113 in amphibious mode was mostly a matter of luck, and made a hovercraft look like an F-1 car for steering. About a foot of it was above water.
This is standard, or you as the most likely to sink one? 
Well, I was informed by a couple of the training NCO’s that my turning was less than optimal, and made me the most likely candidate of the class to sink one. Something to do with causing the thing to get tippy by stopping the track too quickly. The thing was propelled, and steered by the tracks in water, it sort of dog paddles its way around at a few mph, and had a different set of control levers for aquatic steering. Apparently, stopping the track quickly causes the entire machine to tip, and rock a bit. I was for the whole of that day, subjected to jokes about submarines. 
In order to swim the 113 A1 if it wasn’t full of people, it had to be ballasted with an equal weight of whatever to keep it trimmed, otherwise if it was empty it would just nose down and bob around like a bottle. We piled old track sections in the back, and had to generously grease the ramp, and door seals to stop any leakage. The 113 A1 has a bilge pump that runs constantly, and it could or perhaps should, keep things dry enough to stay afloat.
PDF agrees with you, with the advent of present day MBT’s and the host of long standoff smart ,and unmanned weapon systems,all the things that ones sees on the Military channel these days, they would probably not be needed. Given recent events in Eastern Europe, and the middle East, maybe this topic is going to gather greater interest in the wider World.
Soviet Tanks were not all great, nor all bad. (well other than the T-54 anyway) They did have some serious drawbacks in their designs, and equipment. Though I can’t speak for the rest of NATO, the M-60 series had some deficiencies as well. The 60 used a high pressure hydraulics to operate the Turret power traverse, elevation, and depression of the gun. There was an accumulator that was kept at 1200 psi by a noisy pump. This fed the system of lines that ran around the Turret walls, and here and there to where ever they needed to go. This created a fire hazard for the crew. If an incoming round came through and cut these lines open, it would be a blow torch. The 60 was a bit too high, though it was felt that this was a minor problem. The fuel filters were a problem to service, the bulkhead between the crew, and engine/fuel cell compartment would have to be removed to get at them. Its not the best thing to have thin, bolted plates between you, and 500 gallons of diesel fuel. Later, there was an upgrade done to run tubes from the filters back to the top of the engine compartment just under the grill doors. A pair of valves not unlike thermos cooler taps were used to purge the filters. Honestly, no real protection for them, and if damaged they would start pumping fuel into the rear of the Hull. The plusses as I said earlier are good operating range, excellent fire control (for the time) a Turret floor that moved with the Turret a definite one up on the Soviets who didn’t have such decadent luxuries. Every 60 had a nice radio setup, with an auxiliary receiver to allow each tank to communicate with company, battalion, and whomever else they needed to. After Day 1, or 2, the Company Commander could be a buck Sergeant , and would need to talk to the higher levels of command. The U.S. military made a big fuss over the Soviet T-72 Tank, and were very wary of it at first. Part of the fuss was to keep us motivated, the rest was just because they had not gotten hold of one yet. Once they did, it was a case of never mind. I do have to add that the T-72 did spur NATO to begin freshening up the armored forces in W.Europe. New tanks began to show up, even the M-60 A2 (not to be confused with the A1E2 having the missile launcher) the A2 was pretty much a modernized A1 but had full stabilization for the main gun. its replacement, the A3 had a new rangefinder, and fire control, and a wind direction detector added some additional finesse to gunnery. I have to say that its a bit weird to see Tanks that weren’t even out when I was serving on display in parks, and taking hits on gunnery ranges. Gives one to wonder what is on the drawing boards, and hiding away on remote proving grounds waiting for their day.