Please! You think intensity is only defined by the amout of second you hold the weight?
Yes, since slowing the speed of your reps is only one way to increase the intensity of your training.
While on HIT, I use the following intensity techniques: slow reps, forced reps, positive failure, static failure, negative failure, pre-exhaust, ZERO rest inbetween sets.
You have no idea what level of difficulty this type of training is on. I really don't think 99% of people could do it, including you.
The only challenge with volume training is clearing your schedule for a 2 hour workout. It's not only easy but it's quite honestly a waste of time.
As Mentzer said, you can either train hard or long, but you can't do both. And it just so happens that it takes hard work to build muscle. If Arnold trained with HIT he would be doing 10 minute workouts like I do.