My question is, must 'varicose veins in legs' be another T2 page? Or can it be a T3 page? Or should one scrap this format altogether?
The way I understand it, every T3 must connect to at least one T2 and then to the T1 (home).
If your page links mostly from a T3 that is linked from a T2 it could be a T4.
I do not think you would have a T3 that does not link through a T2 to your home page. It would itself be linked back as a T2 in this case. If it is not linked from the home page or a T2 (the very links that define the T2 and T3), it would then be an orphan even if it is linked back to to a T3.
Maybe I'm being silly, but I think our sight structure has to have at least one leg running down (out):
Home T1 > T2 > T3 > T4 etc.
Then at least one line needs to run back the same main path. It's your proof you do not have orphaned pages. You can have other branches to T3s, but must have at least one complete pathway back to the Home page missing no tier.
Maybe I'm missing the boat with your question.