Well, as an exercise physiologist, drumming (e.g., playing a kit vigorously) is indeed exercise. What most people fail to get about what they consider exercise is that it mimics and is a substitute for, real functional work. Your body doesn't care if it's lifting logs or weights. It doesn't care if your 150 bpm cardio workout is from a bike or playing double bass - all your body knows is that, "hey, my heart is beating faster & I need to remodel myself & the vascular system so I can adapt to this workload".
In short, nope, drumming is not running marathons & it's not lifting weights to failure... However, if you're playing vigorously and sustained, if the heart rate is within the ranges necessary to illicit a response (according to my Polar the average is indeed), it is exercise - valid, cardiovascular exercise with all the benefits of "real" cardio. In addition, it uses all 4 limbs & the core for stabilization, unlike running or cycling (little to no upper body). It doesn't receive the benefits of being weight bearing as does running, but neither does cycling.
To conclude, if you're playing vigorously and regularly you're getting a decent cardio workout. You'd never train beyond a certain level - would never really experience the benefits of overloading to constantly push for increased benefits - but the benefits would remain.