Putting aside the fact that I still dislike the lack of crafting for seasonal weapons, I largely agree with you. Getting seasonal weapons while just playing the rest of the game easily is great.
As far as I can tell, adepts don't drop from the tome and neither do double perk drops though I could be wrong about the latter. Would be great if they added a chance for those to drop too.
Fragments are unlocked account wide. You will need to complete the 6 side-quests (those adventures at the lost city landing zone) to unlock all of prismatic aspects, grenades, supers etc. on each alt after the campaign .
Nimesh Patel backed out about a week before and didn't end up performing