Only some parts of progression are required, not all. Like you need t2 EoK armor to make t1 RoS.
If you are group geared and want to survive in 2 zones from the nasty ae from sarnaks, you need to do ALL eok progression. Considering there are only 5 group zones the 6th requiring 2 group raids, that's 2 out 5 zones that require progression to function.
Since there are only 6 zones this expansion. Thats 40% of the expansion your not functioning in (I'm not counting VP, cause most group group players won't even bother playing in that zone, its the equivalent of Plane of War).