I'd be very surprised if in the more accurate lore version he WASN'T a high level druid, if not an archdruis. Probably not a Great Druid, but one of the top three of the Circle? Arundel from IWD was level 14.
I honestly dont quite understand why would he "need to be high level character" ...
I mean feel free to corect me, but as far as i know Druids are not usualy society where "the strongest rule over all". :-/
It actually is, as there are 3 archdruids, and 9 in the inner circle (regular druids), and in order to ascend into that circle you have to defeat the currently seated member. If you lose, you automatically lose XP points that bumps you down to a certain level. That's probably how a lot of shadow druids infiltrated the druid order.
Considering that reincarnate is a fifth level spell, a tenth level Halsin should be able to cast it, and offer it as an option with the caveat of "we have no idea what race you'll become". Lae'zel will be horrified, Wyll may not really care, dunno about Gale, Shadowheart may not care, and Astarion will be horrified that he'd lose his pretty face that he can't remember. It'd feel very weird to have initiates leading the grove, though.
For one, Wyll would definietly care, since there is nothing Wyll care more about than Wyll himself ... and his reputation ... he would hardly be able to continue as "legendary blade of frontiers" when he would become something else.

For two, Halsin is not level 10, but level 5 ... so why are we even talking about this?

If we would start "if circumstances would be different" ... then we can also change circumstances right from the start to being able to pick the "brainbug" with long sharp pointy needle through our ear.

Halsin cannot be lore-wise level 5, because that's way too low. 8+d8*4+ConMod*5 cannot give you 90+ HP, unless he has 6+ ConMod (and that's assuming you roll 8 4 times). He's much more upper-level than that. I honestly don't see why he couldn't be a level 10 other than "well, then the party would be wiped out" (a level 1 party getting wiped out by challenging something ridiculous like a dragon, a company of githyanki, or the master of druids should be happening IMHO, because I quite frankly don't cherish the idea of getting wiped out by a level 1 party when MY party is level 15). Larian has set so that the enemies are levelling with you.
And Kagha at one point had the title archdruid.
I was not aware of this ...
When did that happen?
At least a year ago. Here's the link:
https://www.reddit.com/r/BaldursGat...tandards_for_becoming_an_archdruid_have/Also not sure why you can be a cleric of the Dead Three. Last I checked they weren't much more than glorified mortals that don't die. Who's granting their spells?
Im not quite sure when, but i believe i have heared Wolfheart in one of his lore videos talking about some event when they reached full godhood.
Try to look there.

You're talking about the weird agreement with Jergal, which was pre-Time of Troubles and the Spellplague AND the Second Sundering (basically pre-everything). The Dead Three were mortals in Ancient Netheril times, so their ascent to godhood happened around -360DR. The Second Sundering brought all of the gods back, but the Dead Three were bumped down to Quasi-Deities by the end of the 15th century (remember, Second Sundering ended in 1487DR, so it's been only 5 years), who are basically beings who can't die but are pretty much mortal in every other way. Myrkul is currently serving Kelemvor. Dunno what Bane and Bhaal are doing, but I doubt they'd be able to grant spells. Also REALLY not sure why Astarion doesn't realise that the symbols they see everywhere around the Absolute's Chosens have at least Myrkul's symbol on it, because Myrkul was the God of the Dead for the vast majority of his lifetime and he definitely would've seen the symbol, being a vampire spawn. Myrkul died in 1358DR. Selective blindness seems to curse everyone in this game, since the Gur blithely ignores my PC calling Astarion by his name (not to mention pasty white skin, red eyes, and fangs).
Mr. Bones is just offering resurrection for 200 gold, cheaper than a goddamn revivify diamond.
I dare to presume that cost is there exactly to make ressurection accesible for EA, after all Larian had no idea (at least from start) how often will we die ... and it would be terrible experience if you would not be able to get past first encounter with Intellect Devourers on beach and had no way to ressurect your party members.

In other words i hope in final release this guy will either be removed, or his cost will incerase like at least 10 times as much.
One thing I'd like to point out with Revivify is that the body must be intact. So if your head is burned to cinders, or your brain is bashed in, you can't use it. Similarly, if Wyll's head is cut off during combat, then Revivify shouldn't be able to bring him back, so I guess we are all to assume that no DAO-style murder occurs in this game. Gale's scroll, however, would definitely work to solve at least one member's tadpole problem. It would've created an interesting side plot as Wyll, Lae'Zel, Astarion, and Shadowheart tried to take the scroll. Using the scroll would solve both of Astarion's problems (he's just on the cusp of the expiration date, iirc).
Who's powering Withers' spell? The only guy I can think of is Kelemvor, but the guy was dead long before Kelemvor was even born.