Use polymorph to turn dragons into butterflies, this will really help u.
I've not done this missions so I dont know exactly what to do - but here is how i usually do these missions - save game, turn dragon fly around and destroy a few towers until health low, turn human (if u can land) heal (esp via healing spell), then save, then repeat all.
Save and reload a lot.
Don't let the enemy dragons breed if u can and destroy the nest towers first. Use shield when u r destroying nests.
Stay out of the fight as far away as possible when health is low.
Use ur fire sphere on towers. That's what that is for after all. This allows u to do the job much faster.
Destroy any key generators and fortifications first ( if u can).
Always go for the entrances to dungeons first, this will help u level up a bit and maybe destroy some shields. Sometimes when u destroy all of these the rest of the dragons and towers are automatically destroyed.
Use potions if u have to. My advice is to go and buy like 20, if hte game is about to end then just spend all the gold u have.
To be honest, u shud be higher level, don't waste the rest of the game for nothing. Explore. It wil be better. I am a mage character - so I can face guys 10 levels higher than me, but I take my time, because its better to complete the whole game. U could easily clear out the dungeons quickly instead of struggling and fighting for u life for ages on this one. I know cos i went into Stone's Flying Fortress as a low level character and i really had to fight for it. it is just extra lol
Take it easy because the game is biased, if i am high level (31) now, level 28s cannot hurt me at all!!! that is a little bit silly, but level 35s (especially in dragon mode) can be a real pain, so that's the way the game relies too much on levels, so just make up ur mind about it.
The rest of the orobas fjords missions and dungeons are not that tough so it is possible to clear them out in two full days, or even one, if u level 30.