Yes, you should.
I do intervals. I've been doing six five-minute reps at 165-176 BPM, with a three- to five-minute rest in between. Those are hill intervals, on a road. I've also been doing race simulation intervals, with run-ups and dismounts, for about the same duration as the hill intervals. You should ride on the grass/ sand/ off-road a LOT, regardless of your interval schedule. I also do running hill workouts, but that's not necessarily for 'cross, even though they do help (I just can't kick the running habit, no matter how much I spend on biking stuff).
A good portion (like, all) of a 'cross race is spent in the hurt zone, so you should be accustomed to getting there, quickly, while still being able to control your bike and your laughter. Intervals are good for this.
Just don't go ape-sh## crazy and do these more than once a week. Cornering and dismounts need love too.