Did you clear out the opponents on the mountain path, as well as the beach you can swim over to behind the anti-dragon defenses?
Trying to level in the fjords I also had trouble with the first group of level 21 imps when I was level 17, but only needed another 4k experience to reach level 18. I found the creature much more helpful after I switched from a level 6 warrior head to a level 2 ranger one (didn't have a mage head at the time). It was more aggressive as a ranger/mage, and also made a better shield, since it didn't move around as much. In Broken Valley there are not as many rangers/mages, so a warrior creature can do fine, even if it is slow to react sometimes, and doesn't use Rush Attack very often.
I have not played a ranger (or mage), so I'm not sure why you would be having that much trouble with a group of opponents the same level. Even if you hit and run back out of range, you should be able to whittle them down one or two at a time. Maybe try the Hide in Shadows skill, to get close enough to take out a few with explosive arrows.
