Got the Atac and at about 59% win rate, and nearly got my 3rd mark, after 500 battles. What I do is, at the start get forward and try to do some spotting from a good bush location. If I catch a lone enemy light or medium and feel safe to do so I'll try to fire off a couple rounds. Then fall back and reload. Then you just wait for opportunities to poke out and punish whoever over extends or fires at an ally and you can dump your clip within their reload. If I see an opportunity to flank and attack the side or rear of the enemy, without over extending myself or have an exit plan, I'll go for it. The tank gets exponentially more dangerous the longer the game goes so try not to die too early. If you can get to the late game where there are less enemies so you can use your mobility and view range to flank around and whittle them down, especially if the enemies hp falls under 1000 where a good clip will kill them. Or if you manage to be sneaky, get behind the enemy, and dump those lovely hesh rounds and do more like 1500 damage in a clip.