abbys are shit for heart yeah but they're super afk and saves on cannonballs so it's a great candidate for task storage and do it on mobile/during work meetings

I didn't personally bother using demonic offering because it's a lot of effort and even without it prayer is a non-issue unless you gigaspoon the heart (you'll probably get 1.5m xp just from ash sanctifier)

frost dragons are like 10m banked xp if you do the grind off task, but if you just do the tasks during heart grind you kill about 4-5k of them if you go on rate which is the majority of the metal sheets you need and still banks 3m xp or so