Post 30 they fall off hard, the XP TNL starts to greatly outpace the total XP you get under a scroll(80k+40k bonus). By mid 30s, a scroll, with rested XP isn't even a level. A bit after 40, you'll need 2 scrolls with rested XP for both to level. 49-50, you'll need 3 scrolls with full rested XP for all 3 and you still won't get to 50. And your XP per hit gets comparatively horrible each level. Even with scrolls you'll get a fairly large surplus of raw materials unless you use the extremely inefficient gathering leves I mean you only need like 8 to go from 49-50.