Fire Temple is a major stop for progressing through your 30s. While there are only a few quests within the Fire Temple, they offer very good XP and gear rewards for how easy they are to complete. If you and your friends are running the instance anyway, be sure to pick up the corresponding quests!
More information on the Fire Temple Entry Quests can be found here.
Asmodian Entry Quest
Elyos Entry Quest
Monsters within the Kyola Temple in Eltnen have a chance to drop
the quest-starting Fire Temple Key.