Well, laters Migi, it always a joy playing with ya.
The problem is, people exploit things which eventually causes them to get nerfed. Imagine if some Armor Company player started off with 3 Shermans with Crab Frails. Those Crab Frails will rape infantry in a very gory and entertaining way. However, there are very few people who uses Crab Frails so it doesn't get its price skyrocketed. Basically, any popular strategy that is simple, effective, and difficult to beat gets labeled as overpowered by the opposing team. Repair bunkers wouldn't be so bad if we all limit ourselves to building like 1-2. But by building 6-9 bunkers, you effectively make that aspect of the game overpowered.
actually i would say about 50-70% of shermans i see lately have crabflails on them.. these are GREAT anti infantry, but they are also essential anti mine items. I dunno how much they could truly 'nerf' the flail due to the amount of mines around the map these days... but its anti infantry ability is insane to say the least.