2 is a lot harder than 1. The game doesn't seem to have a limit but I assure you as someone that has had plenty of parties rage quit from 2 you are going to need most of your team be level 50+.

I managed to run FG2 today (normal) with my 460 cp DPS, a 50 cp tank then healer and stam dps both below 50. We did die repeatedly on one of the bosses even when I explained the chaining and one shotting mechanic and how to stop it. But this time at least my party didn't rage quit and we got through it. (also helps if it doesn't chain me first)

The tank seemed experienced but the stam dps was just spaming bow light attacks, the healer apperently had the glitch where he can't see the characters of his teamates so he couldn't rez us.

A number of dungeons have Dps gating mechanics that really need (especially for veteran) skill, levels and cp bonuses.
The typical issue with low level characters is just not having all thier DPS skills and having them leveled and morphed and CP gives characters a lot of damage mitigation which is important for tanks.