When you increase the quest difficulty, the chances of getting a legendary/mythical weapon increase (by little) as well.
I personally would recommend playing TGK quest on 300% with a good team of 3-4 players that got miniguns with high PVE. If you go solo, then do 200%.
In my opinion, Scrider is soloable, but few things:
- it takes a lot of time
- ain't worth the effort
- low chances that anyone will be able to beat the boss after 20%.
In general, I'd recommend playing Scrider with 3 other players on 100~125%, 'cause in average you'll be able to beat it within less than a minute and get good drops after 30~60 mins in the room (tested it multiple times
)
The best difficulty for solo quests like School Quest/TGK/FGK is 150~200%.
When you increase the quest difficulty, the chances of getting a legendary/mythical weapon increase (by little) as well.