Okay I have looked at the new factions and they are all bad. I don't like them and I liked the old factions plugin where it was /f show and stuff. Which version of factions works on 1.8. (The /f show factions)
Only the versions built for 1.8 will work on 1.8 servers. This is because so much of the minecraft and bukkit api changed in the 1.8 update that plugins for versions lower than that are often not compatible.