I have to agree with the slayer newbie on the defender part. On most tasks, no slayer monster that you don't pray against you don't need all the defence bonuses that dfs gives. With defender, you get three things. Decent defence, excellent attack bonuses and very good str bonus. Dfs gives 2 or 3 more strength bonus and much more defence but you don't need that. The attack bonuses > defence bonuses on slayer tasks.