He is incompetent leader, who even admits that himself. It's not a dumb story, it's normal realistic story about how people do make mistakes.
Yes ... Halsin certainly did a misstake ...
But i would not call him incompetent. :-/
- We dont know how ambicious Kagha was while he was around ... after all, his presence alone was more than enough to cool her down.
- The same we have no idea what creatures, or how often attacked the groove ... i mean, we know about litteraly two attacks of Goblin scout parties ... one is that Aradin lead there, and second one is that where was Sazza ... yes, we know that Drow with Goblins attacked Halsin and Nettie, but either i simply forgot, or there is never told where they attacked them ...
Was it another attack to Groove itself? Or they simply attacked them in wilderness, when they were i dunno ... gathering herbs prehaps?
Personaly i thrust the second option more, since:
1) The corpse is in the room, that is acessible from secret passage and locked.
2) No one else seems to know about the tadpole, nor the Drow.