Hmm well the server shutdown from the PC version isn't that new .. just wondering, that you guys noticed it that late.
I read it already in the beginning of June and decided to platinum it.
I can confirm, that everything beside the Coop Campaign and the Dungeon Leader trophys can be done offline.
The time estimates are kinda confusing, what you mentioned, big_bob.
A campaign run can be done in under 20 hours.
"Summoner" - Summon 1000 creatures as Dungeon Master - your mate runs to the end and wait before the stairs and you keep spawning creatures, until it really laggs hard (I would say 100 should work for 1 run) - takes maybe 1 hour around (some creatures spawn slower, some faster .. just try out, what works best for you)
"Dominator" - Possess 500 creatures as Dungeon Master - you can possess and depossess the same monster over and over again so this maybe takes like 30 mins to maximum 1 hour .. depends on ur skill to press commands fast
Overall I can say, that those loading times are really awful, but the story is worth it .. well maybe not 6-7 times but at least once
And to max every characters level is really annoying .. wish ya good nerves for that one