What people do not understand about CPU bottlenecks is they happen on a single core. You can have 25% CPU usage, and still be CPU bottlenecked if the game only uses 2 cores with an 8 core CPU. Lots of games are CPU bottlenecked, even with 50% usage. You have to look at the individual cores to know if you are bottlenecked or not. You may also want to look at the GPU usage. If it isn't near 100%, that is usually due to the CPU, which is a far more accurate way to see if yo have CPU bottleneck, than looking at the total CPU usage.
ARMA games are known to be hugely CPU bottlenecked.