I did Elder on a playthrough last night with a lvl 2 finewood bow loaded with fire arrows. Lvl 2 troll armor.

Provided you dodge the roots etc. thrown at you, it's a simple wear down. I might suggest using a stamina tonic and fire off the Eikthyr ability so you can jump and run around. It helps. Another neat trick is to light a heap of fires around the place, try drawing him into it. If you're good with parry and like a thrill, charge in occassionally with a bronze axe.

Just monitor your health and stamina and you should romp it in. GL