Soooo what exactly should I be melding as a WHM? I'm only ilvl 299, but so far I haven't melded anything because I have no idea how any of this stuff works, and the game doesn't bother explaining any of it. Like my first instinct is that I should be melding mind, but apparently that's not the case? Why do they make this stuff so stupidly complicated that you have to look up complex calculations online?
Does melding even really matter?
When you open the meld menu, say at the materia melder npc if you don't have crafting, it'll tell you what you can meld. Generally speaking, whatever is on the item can't be melded or is heavily capped. That's cause of the stars weight formula, where each stat has a maximum amount per ilvl, and if the stat is directly on the item, if it's primary it's capped and if it's secondary it's close to cap. So you can't meld mind on pretty much any mind gear, making mind/int/dex materias pretty worthless in general. They've been used in the past on vit crafted accessories to reach certain hp treshold for hard content but who knows if that'll be the case ever again.
I think I'd probably meld det, and if you can't meld det, crit or possibly piety for learning content. DH is better for damage but also doesn't do anything for heals which seems kinda meh as a choice. For SCH, crit over det probably since you still want these crit adlos.
As for stacking Dhit, everyone's been saying that for a little while from what I've seen. Not a big surprise, I think the surprise is more that det is better than crit currently. Maybe next tier it won't be.