It's not a terrorist attack unless the primary goal is causing terror. The primary goal here was clearly causing damage to Hamas' command structure by putting a few thousand militants in the hospital, and also literally blowing up their communications network.
What would you killing 8+ peole and wounding 2800+? Were it any other actor, there would be absolutely no hesitation in calling it a terrorist attack.
You know who uses pagers? Doctors and nurses. Are they legitimate military targets? Let's just say that a Hezbollah or Hamas commander was killed. What's an acceptable civilian dead or wounded count that takes it out of the realm of a terrorist attack? How many is too many?
I think that they are inspiring terror, but terror against operatives. That's a good goal. Terror against civilians is the problem (according to our modern moral code)