Some more thoughts --(a) you said something about getting back to full strength. does that mean that you're waiting/resting/camping? if so, the monsters *will* just respawn, probably as fast or faster than you can get rid of them. having one or more regenerative items really helps in that regard (both hp and sp regen).
(b) if you have the option, turn the difficulty level down. that won't help so much with the monsters already spawned, but it may reduce the number and type of monsters spawning in the future.
(c) as llevram said, it's key to get into a more defensible position -- some of the critters are fast and will surround you, making battles harder than they need to be.
(d) most of the monsters in bayjin are most vulnerable to fire. stock up on fire magics.
(e) if you're having a lot of trouble with rynjin spellcasting, you need to boost your mental/divine resistances. cast soul shield fast and at a high level, and/or pick up some appropriate reistance items.
15 battles! I think that would definately do me in also. I have had the same thing happen to me on the road a few times... I finish killing 7 juggernauts, and 9 plants show up as I am delivering the final blow to the 8th juggernaut. Then I kill 7-8 plants and Trynnie outlaws show up. Then bats arrived. I was very frustrated since I just wanted to go to Arnika to sell stuff. Running is an option, but I only like running if I feel like I can't win the battle. And running each round in battle is still MUCH slower than just walking around out of battle.I would say to try following the advice already given and run into a hut. Then maybe less monsters will see you also. I don't mind fighting tons of monsters when I am trying to level up, but when I want to explore, there is a point where it can be just too much. I always prefer to have fewer encounters of more difficult creatures.
Don't give up on the game. The whole game isn't that way. And be sure to set portals with all your spellcasters so that travelling can be done in seconds instead of hours.