Couple of points that might help you:
1. Never fight monsters more than 1 higher level than you - if you're doing this, chances are you're missing out on monsters elsewhere who are more appropriate for you.
2. Pet Pal! Worth tons of XP, not taking this on one person costs you a lot of experience from quests you cannot obtain otherwise.
3. Mixed parties work better in this game than deciding "well fire mages are best so I'll rustle up four of them." Everyone has strengths and weaknesses - a balanced group is great.
4. Steal stuff. Invisibility/Walk in Shadows lets you rob people in broad daylight, which in turn lets you buy skillbooks and better weapons/armor so you'll do a better job surviving.
Finally, the stuff in Cyseal is level coded for your ease: