In the runespan go to the island (13,14,16) where all the levels 83 - 90 hang out. If you dont care about points stay there its like 10k hour faster xp but less points. @ 95 move to the soul island.
Or if your talking about farming nature runes/deaths then i suggest you just buy a 99 rc account as you can bot the runes for 2 weeks (about the time to get 99 rc botting) and make a profit plus have the account. there's like 10 99 rc accounts for sale right now.