Just in case anyone is wondering what the absolute MINIMUM expansion progress requirements are, after some experimentation across a bunch of characters I've discovered the following.
CoP: Complete 3-2 "A vessel without a captain". The CS at the Ducal Palace unlocks sequence leading to acquisition of Tenzen II and Prishe II trusts.
ToAU: Complete mission 11 "Imperial Schemes". (Watch CS in Salaheem's Sentinel's day wait after completing "Astral Waves"). This is sufficient for Nashmeira/Aphmau requirements and also Rhapsody in Crimson KI.
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WotG: Complete mission 7 "Purple is the new black". Win black dragon fight and watch all CS afterwards. The log will show mission as "In the Name of the Father". This completes Lillisette's trust requirements after you have the first CS with Cait Sith at Batallia maw from RoV. You will receive the trust after the CS with her talking about "dreams" upon next zone-in to S.Sandy[s] by any means.
However, only after seeing the CS in Walk Of Echoes (Use Xarcabard[S] entrance) and returning to the Batallia Maw will you be able to progress into RoV mission 2-17 "Sacrifice". Unsure if the WoE CS is absolutely neccessary, but its a simple additional step with the HP just outside.
RotZ: Complete mission 4 "The Temple of Uggalepih". Again, all CS must be watched after BC, log will show "Headstone Pilgrimage" as current. Everyone seems to forget about this, but without it RoV 2-25 cannot complete!
This achieved you may push straight through to the current end-point RoV 2-41 collecting all remaining trusts and Rhapsody KI's along the way.
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All info confirmed 100% correct @ 22/8/15.
Last note: Passing these minimums may block you. I'm posting this as a minimalist guide for somebody wanting to push a fresh char or mule through.