Let's think about this, for a second. In previous games and stories, the archdruid is typically the strongest, wisest druid in the grove. In the original BG games, you are given the ability to have Jaheira challenge a druid to be head of the grove. You must face the archdruid, essentially, in combat with nothing but like a quarterstaff, and if you win, you become the head of the druid order there. So it makes sense that the archdruid would be the highest level character in the bunch.

The Emerald Grove has like maybe two dozen druids. Maybe more. I never actually counted them. You and your companions level up from 1 to 4 in just a few days. So let's say the grove is filled with druids varying from levels 1-4. If Rath is the most powerful over all these other, lesser druids, making him like 3rd in line, then he should probably be at least level 5. If Kagha is stronger than him, and so much so that he won't even try to challenge her, then she should probably be at least a level or two higher than him. After all, a level 5 character might challenge and beat a level 6 character. So Kagha should be maybe 6 or 7 or even 8 so that she is quite a bit above Rath. But let's say she's only at 6. Even still, Olodan should then be, at minimum, level 7 because Kagha is scared of her and acts like she is her great master and teacher. This would mean that Halsin should, for all intents and purposes, be at LEAST level 8 so that he could be more powerful than Olodan.

So how is that so far off from my original suggestion? It makes sense that Halsin is at least level 10, Olodan like 9, Kagha 8, Rath 7, etc.

AND, I might add, I find it interesting that WotC DID actually give us some idea of how powerful an Archdruid should be. At level 20, a Druid receives the Feature Archdruid. Thus, it is suggested that an Archdruid should actually be someone at level 20. I do not agree with this, because then every archdruid at every grove would be a godlike character. You'd never have an archdruid in any story because they'd be too overpowered. So I don't even know why they'd call the Feature this. But, regardless of this, I think it is completely unreasonable to think that Halsin would be anything lower than level 8, at bare minimum. Especially if he's supposed to be such an awesome healer, he should be at least 10, if not higher.

And finally, if you actually look into the stats of a powerful druid, I really struggle with an archdruid like Halsin being overwhelmed by goblins. I created him as a level 10 druid, just to see what he'd be like. The man's OP against a bunch of goblins. Even if you buff them, Halsin would wipe the floor with tons of goblins. Only IF the goblins were being assisted by, say, a powerful Hobgoblin Warlord or Drow Cleric would he be defeated. It makes no sense to me that he turned himself into a bear and got captured so easily when he could have blasted them with Ice Storms and Nature's Wrath, or he could have conjured hosts of animals to help fight them off or created Walls of Fire to aid in their escape. There are SO many things he could have done to fight them off and wipe the floor with them.

There are only three reasonable explanations, therefore. Either Halsin is a weakling of an archdruid, and the Emerald Grove is a piss-ant druid grove with nothing but weakling, baby druids (which means Larian GREATLY overexaggerates the importance of the grove), OR he let himself get captured so he could learn more about the Absolute, OR he was teamed up on by more powerful enemies than a horde of goblins (such as a more powerful Ragzlin and Minthara).

Either way, current strength of these characters just doesn't make sense from a story perspective.