Plenty of hard tasks to use mage on and barrage in katacoumbs and kree you can range. Don't focus on one to make it easier and if you want to then use anti venom....
I think you still dont understand... all these monsters are easier to kill with slay helm. More kills per trip and ect. But only zulrah makes that you do less kills in trip with slayer helm because of that venom. Which these 7500 slayer points should make disappear. Who the hell even do hard task after lvl 99 slayer? Maybe who want 200m exp only. So talking about hard tasks are absolutely pointless..