personally i think grinding the first 10-15 levels is just as fast as questing in a good spot as classes haven't gained of all their strong skills yet . i think after this you have to asses how hard each quest would be for a bot to do individually . For instance a quest like the one to run from razor hill to XR is a good bot quest youll be passing those locations and have little risk . where as going to the top of a castle in a densely populated area is just to risky to be with unless you watching your character whilst botting.
TL:DR Simplistic Safe quests are worth it but in a aut