Originally Posted by
druid138
This isn't scientific, and it will depend on what kinds of resources you have or don't have, but my rule of thumb is to level 4* and 5* hearts to the level 30-40 range and not level 3* hearts just because of the time it takes.
My focus is on maximizing the number of Heart Soul rewards, so Tier 5 is the sweet spot. Tier 1 is also better than Tiers 2 and 3 for Hearts, when I'm burning regular stacks.
Not sure about the best strategies for getting Ironite drops. I haven't paid close attention to that so far.