I have a single female ranger at lev 34 now. I am having no difficulties even at the ascension peak. My strategies were: - Having stamina regenerators, casting stamina spell in the mid of the combat.
- Avoding monsters surrounding her, by walking right at the beginning of the combat, if necessary. Sometimes running past the mosters at vast areas like Arnika-Tyrnton road or swamp.
- Having infinity helm from Ferro as soon as possible (happened at lev 25 though) Great spell, stamina recoverer.
- Using canned elementals
- Not resting at all. It is day 20 and I'm ready to finish the game.
- Using easy game setting 
- Avoiding paralysis or knock outs at low levels bec they are equivalent to death. Using artifacts to increase mental resistance.
You definitely have to use an npc to get the martens idol. Unless of course you will kill croc before hand.
For fun I got company as Sparkle (another ranger) before I go to ascension peak. She was at lev 6-7 by then. She were killed several times, I resurrected her in the combat close to the end to make her get the exp points. She were killed 35 times and got 3 kills in the meanwhile. Finally she reached lev 20 after a few fights. My ranger was at lev 33. The fights got harder just to keep her alive during the combat.