Have you lowered the game difficulty? Even on easy level 30 is a little low for the end of the game, but it is possible.
Charms and temporary boost potions can help. Have you enchanted everything you can with level 9 or 10 enchantments? Level 10 enchantments require a rare malachite gem, but are generally not that much better than level 9; the healing aura enchantment always requires a malachite gem.
The
Character Optimization topic, etc, may give some ideas for ways you could change your skills to a more effective build.
If you recently turned in a bunch of quests, you could reload an earlier save, max Wisdom (equip Rothman's Bow, the Talisman of the North and the Wishing Well bracelet, if you have them), turn the quests in again, and then reskill when you are ready to head to the hall of echoes, to put the points in Wisdom to better use (assuming you have the gold to reskill another time or two). If you are not reasonably close to level 31, though, this might not make a difference.
Have you checked all the merchants for upgrades since you last leveled?
If not, if you save before running the crosshairs over a merchant, you can trade and then reload if they don't have anything worth getting.
The merchant in High Halls starts selling legendary equipment once you get to a high enough level, though he doesn't have a huge selection.
I assume you checked your quest log for things to do, and ran/flew around looking for areas you may have missed?
Have you finished off all the flying fortresses?
There are a couple areas in the game where opponents can respawn, but you may need to reload an earlier save (see
here).
I need help with a battle (Spoilers) Ygerna's memory
help im stuck in hall of echoesAnother..Hall of Echoes question
