Chary wouldn't be a hard solo without the hitting like a kraken club, it would simple be a time consuming solo, there's a difference. And it's def isn't really that high.
As for OP, I swear the sigil xp bonus is broken or something, I should try testing it out myself, lol. It's never seemed to work for me. But yeah, it's probably a bit much to ask, but if you could try doing it with 4 people instead of 5, that would probably solve our question of the xp bonus, hehe.