Well if you are used to Operation Flashpoint, Ghost Recon and Rainbow Six, it is *lack* of realism that is the problem, if anything. I think it is a fun shoot-em-up mix between those and the even more dumbed-down games like Counter-Strike.
As far as the Tigger vs. Sherman, it is about balance -the former's strong armor is countered by lack of maneuverability (slow speed, poor suspension) and slow reload whereas the latter has weak armor but is fast, stable, nimble and quick to reload. So, if in a Sherman use it to its best advantage by keeping on the move -you can literally run circles around (or large arcs or quick passes, anyway) a Tiger while firing at it and avoid getting hit. Try to get it in the ass, as all tanks. Conversely, if in a Tiger use its armor and firepower to your advantage by rotating in place to keep the front towards the enemy and time your shots well. It is also effective to charge other tanks, besides the Wolverine, and ram them.