For me, the main thing that goes against the spellweaver is that you get a perfectly fine one early in the game.
As far as "NWN2" vs Drakensang goes, for me it's a hard call. I hate how NWN2 force you to take NPCs, I dislike how much emphasis it put on the ai. Controlling a 8 characters group (not to mention equipping/upgrading them all) is a nightmare. And since DnD got to 3rd edition, the game became too much about multi-classing/prestige class up to a point it stops being interesting. Drakensang gameplay and battles are generally more fun. Areas are more interesting to explore, wilderness doesnt seem as much limited (even if it's still a far cry than what we could find in a game like BG. I blame 3d). Plenty of small side-quests that make you return to some areas in Ferdok... Unlike the city of neverwinter, you at least get to know Ferdock somewhat.
However, I find NWN2 equipment, spells and NPC more interesting.
For the Spellweaver, it's not that soon in the game, depending if you find it soon or not in the area she is. Another point is that if she is your lore character, your character which is always in the party is a better fit. Finally unlike your own character she won't be able to use the fire set and that makes a difference in the last quarter.
For NWN2 vs Drakensang, I agree on many points you quoted but disagree for:
- Force take some NPC during some part of the game is an excellent game design for me. This give them more personality because it's weird when they are just puppets you pick or not. If you get attached to one, when he leaves it's a bit of nice emotion, if later he cames back it's a bit more emotion, it's a good way to diversify a party without to let the player have decide to reject some NPC ha already get attached to.
- For companions, it's for me a strong points of Drakensang, even if not all are as well done. NWN OC and MotB, goes too far and make them heavy almost a burden to manage. Also I feel the companion mechanism in both OC and MotB not a fun gameplay and you don't need so much dialog to make attaching a companion, MotB is great but on this point a failure. In the end for me it's a large plus in favor to Drakensang even if not all are enough polished.
- For the equipment I like Drakensang choice without ton of magic stuff at every corner. There's also many quite cool hats that NWN2 don't have! Also the NWN2 crafting system is so unclear and boring when it's cool in Drakensang.
I have other points for a Drakensang vs NWN2 but I won't go further. For me it's also quite hard to choose, I bet this will depend when I do it, now it could be MoTB, Drakensang, NWN2 OC.