Well if that is the case then a paradigm shift is even more desperately needed. I'd assume, though, that the defensive doctrine naturally is better in friendly territory from 88 guns and FTFL and all that.
Yes, for 30 seconds it becomes entirely Defensive and tied to own territory. Defensive is just a name for it from VCoH. Its abilities of defence are pretty non-existent. None of the doc abilities require you to stand on your own territory therefore they are not tied up to stand in defence. Just because they have 88 doesn't entirely make them 'defensive' as 88s can be used offensively as well and they excell at it. It is that very long range AT your infantry requires to counter kiting light vehicle/armor responses after a successful push. It is also a solid brick wall behind your frontline and works as a fall back point where you can safely retreat to.