I can’t think of another Grimoir in the game that requires as much of an unavoidable time investment as this one. Sure the ones with jumping puzzles can potentially take a while, but they can also be done in a few seconds.
This one tough adds up to 15 minutes to the map on Legend compared to going straight from Tome 1 to Tome 2. Because the amount of extra distance you need to run to get to it and back easily results in 2~3 horde spawns, same number of Special sets and tons of idle enemies. Not only that, but the areas you cross through for it are not the best to be fighting in as there are very few natural choke points and almost no resources.
2nd Grim of Warcamp is the 2nd highest unavoidable time investment Grim and it doesn’t compare to this one. It’s a minute or two at the most of extra time to the level, which means at worst you get either a extra horde or set of specials. 1st of Convication of Decay can take a minute or two of extra time depending on switch pattern, but again, doesn’t compare to 5~15 mins for Athel first grim.
Now I get that it was placed there to force players to traverse the admittedly nice forest, but balance wise it’s an absolute outlier. The easiest fix would be to add maybe one more decent resource node on to way to or from it’s position, or to move it slightly closer. But as it is, unless you’re in a highly coordinated group, I see no reason to risk so much for this grim.