Who says they weren't affected? The two cases when we actually have characters keep track of an extended period of time, the times they list disagree. There's no way of telling the flow of time outside in Daemonheim. No regular cycle of the sun to count the days into years, and an ever looming madness to further jumble one's perception of time.
In the M. and Thok letter 1, it's established that the Fremennik Seers placed a spell upon the entrance to Daemonheim that made anything but the most basic clothing that crosses it too heavy for even Thok to carry far. In the Letter from Brundt, it is established that only after Thok and Marmaros returned was the call put out to bring adventurers to Daemonheim.
Yet in several of the endings of the Vengeance Saga, the surviving Forgotten Warrior manages to leave Daemonheim with her gear, apparently experiencing no such effect of the spell. This would indicate that she left before the spell was put up. The fact that she faced an adventuring party within Daemonheim, however, would indicate that they entered after the spell was put in place.
There's also a distinct difference between Lexicus and Astea's noting of 5 years passing in Daemonheim, with Lexicus, who was stationed far deeper, noting that he wouldn't even believe they'd passed if not for a calendar he or Astea (on her visits to him) had marked the days off of. Considering Lex could only know the days passing from the words of those above, whose to say that the flow of time in his area wasn't flowing slower relative to that of the surface. Granted, it could just be the standard turn of phrase (has it really been a year? I feel like I saw you only yesterday), but that's less fun to think about.
And, of course, there's Gorndaban's odd account in the latest lore book. Such as noting Bilrach bringing the Ritual Stone back from Freneskae and bringing the Chelon-Mah back (both in the wrong time-frame), but making no note of Moia's visit between these events.
11-Jan-2018 00:38:28