The fame is nice, but by the time I get around to building it, I need hundreds more fame to get the next hero. So how much value comes from 1 fame per turn?
If you're playing with Henchmen, that's enough fame generation to build one Henchman every 20 turns. I think Sions might also cost fame, but it's been a long time since I bothered with them (last time was in E:FE), so I don't know. Other than that, it's not particularly helpful, especially since I don't really have a need for more than two or three champions to act as army leaders.
The experience gain is also nearly worthless for anything but extremely low-level champions or champion-type units, as even at level 4 you're still looking at 54 turns for enough experience to gain a level, and the more levels you have the worse that gets (by level 6, we're looking at nearly 100 turns to gain a level; by level 10 we're looking at more than 200 turns to gain a level; to take a champion from level 1 to level 4 like this would require 69 turns, and that won't even be a useful champion except as a governor). Even with a big clump of champions all in one stack, there's more benefit to going hunting for small packs of wandering monsters than in sitting in a town with the Adventurer's Guild, at least assuming any such monsters or their lairs are left on the map. If the goal is to make it possible for champions who are only slightly short of the experience required for level up to get that extra level, it meets that goal, kind of, though if there are any monsters wandering the map or any quests left to pick up, doing those would give you your level-up far faster. If the goal is to give you a way to level your champions when there are no longer many monsters on the map, it fails terribly.
If it's meant to be a way to allow you to level your champions up once there aren't many monsters or quests left on the map, perhaps it should gain the ability to spawn generic quests (for example, Farmer Bob says there are trolls in a cave near his lands; go kill them for 25 gold and a bit of experience). After all, an Adventurer's Guild sounds like a place you'd go to hire some people to take care of a little problem like that. Or the experience granted per turn should go way up.
But since I don't usually have much need for more than two or three armies each lead by a single mid- to high-level champion, I don't really care about the others I have camped in cities anyways.
