Ever since I first played through the game like 15 or so years ago, I mostly gravitate to the same party, being:

Me . fighter
Ulora/Phaedriel - archer (the only companion swap in the game I usually do, Phaedriel is just a better archer than Ulora when you meet her)
Gyorn - fighter
Naidi - archer
Gloern - fighter
Merik - Nature mage
2 mules (right away from Stonebridge).

3 fighters, 2 archers, 1 mage to heal/buff and add supplemental damage when able. 2 pack mules so I can pick up and sell absolutely everything I find with minimal backtracking, and also to keep the XP distribution of the party tighter. 5 or 6 fighting members seems to be optimal for somewhat keeping up with the gear and spell requirement curve in single player. Any more, and wearing top end gear would not be really feasible.

I find more mages extremely tedious to manage/use efficiently, on top of being pure glass that falls over instantly the moment an enemy looks in their direction. You also have to target farm XP with them or they fall extremely behind your fighters/archers, so having to do it with 2 mages would be very tedious. Gearing one mage is also much easier than two. I always think hard of swapping one mule for Sikra when I get to her, but at that point, I just don't bother and finish the game with the main party. Also, having the final party composition from the moment you meet Merik feels nice. Adding new party members so late in the game doesn't really feel good. The paid ones are very expensive late in the game and non-paid ones are kind of superfluous too.

Merik is probably the one character I'd never drop, as he feels pretty integral to the main plot.

So, anyone willing to share they group composition for the campaign?

I just entered the DS specific thread, because I started DS1 a few days earlier, and I wanted to see what's in this thread. I will play all DS games back to back. It will be my second time playing the series, after 3 years I think. I will post their plots too, if I manage to write them in a right manner!
To answer your thread's question, I soloed DS1 and DS2 at the first time and I'll do the same now (normal difficulty, archer). I accepted story-wise companions (e.g. Ulora, Gyorn, Gloern), only to release them at the next establishment, and I had only packmules following me. Currently, I'm 13 h in DS1 and I just got in Glacern.