Cycling Fitness / Training Advice

Think so. Might not have the time to do it but if you can you get increased capillaries, mitochondria and muscle fibres etc => better lactic clearance, more power before carbohydrate burning blah blah.

Even if you're training for 45mins CX it still benefits just not if it's at the expense of not doing enough intensity too.

That's the key thing I think. Zone 2 rides are probably something you do if you've got the time for more riding after planning all your (achievable) quality work outs for the week.
I don't think the Long Steady Distance approach works for those of us who don't have much time for training.

I have about 8 hours a week training/riding (for 10mile TTs). The NP for my commutes are in Z3/4 ( i commute in/out a valley) and then intervals in my training sessions are done at Z4/5.
If i had any more time for riding it would definitely be at Z1/2 so as to not bust my TSB, but as it is I don't have the time for the extra riding.