I tried to play through some more of the campaign today, it was going fine, then a group of infantry (Who were scripted to spawn from the edge of the map as a way of annoying me) rushed my base. I had a Sherman right there, so no worries, I let it do its thing.

Five minutes later, i go back to my base there and all 3 units are still alive, with about 4/6 soldiers alive in each, with my sherman firing away like a moron, wearing down their healthbars one by one until the game decided they were dead. It was infuriating, my sherman was within 10 feet of the bastards, and it couldn't kill them because the game arbitrarily decided that these troopers could survive 30+ rounds from a sherman. In World War 2, if a tank rolled up that close to a unit of soldiers it would turn them into pulp.

I think Men of War has spoiled me, but I find nothing about 2 units throwing bullets at eachother in the open engaging or fun. Would an easier difficulty do anything to remedy this? Are there any mods that make damage a bit more realistic?

Sherman tanks (and tanks in general) work much better on the move and micromanaged; if you just let them sit there they're not very effective; they also seem to be more accurate on the move. This is relatively accurate to how tanks functioned in WW2 itself as all of the semi decent tank commanders starting with Guderian used tanks to cut through enemy lines and create extensive penetration where infantry or artillery could not; Guderian's "charge" as part of the Manstein plan is the whole reason for the debacle at Dunkirk and the failure of the British Expeditionary Force. Company of Heroes only operates with a small number of units but all things considered it does so with a fair amount of historical accuracy; you can pretty much annihilate anything and take very little damage yourself if you have enough Shermans and are good enough with micro managing them, up to and including the Tiger Ace. Of course non regular Sherman tanks aren't all that effective in this regard; though the Callipso I think it's called is pretty damn useful.

If a tank just sat around stationary for some strange reason it would be relatively easy for infantry to avoid dying to it, additionally the accuracy of tank cannons at very short ranges is incredibly poor; they work best at medium ranges. The tank isn't a Starcraft unit and it's not going to be 100% accurate all of the time (of course the original Starcraft actually did have some elements of accuracy depending on terrain, but 2 doesn't). If you'd like a corollary for what you did Manstein cites (in his memoir Lost Victories) the commitment of Hoth's 4th panzer group to the battle of Stalingrad as one of the primary reasons for the defeat, as the tank group would have been far more useful in the surrounding areas as opposed to the stagnant and immobile siege conditions inside the city; an unmoving tank is essentially a sitting duck and forfeits the primary advantage of mechanized warfare.

http://www.amazon.com/Lost-Victories-Memoirs-Hitlers-Brilliant/dp/0760320543

It's definitely more RTS'y than tactical like Men of War.

I would keep your tanks on the move and use them with other units if you can.