Regarding this list, the initial zones level range is fine, but once it hits "Smouldering lake" and so on with all those 50+, 55+ 50-60... I mean there are like 6 zones where you aren't supposed to gain more than 5 levels according to this list? doesn't make much sense to me. I've done 2 playthroughs ending around 90~ (not including dlc content) and had no problem summoning or being summoned. The only farming I did was for some weapons or to get an ember back helping someone doing a boss.
I mean if you are 70 at the end of the game either you are really bad using up your souls or you are really effing good at this game and you are saving those souls to buy all the stuff plus duplicates.
And this list doesn't take into account the 2 dlcs zones. The amount of souls you get killing stuff on the ringed city zone is ridiculous (after the two demons boss).