Recently I had to resort to skull damage (just because the last week’s campaign requires Khetar troops, and most of them uses skull-related skills). I didn’t do that since scaling troops appeared, so was surprised why it’s so ineffective.
After some research I discovered that skull damages either overlooked long ago, or deliberately nerfed to the ridiculous levels.
Any mana crystal cluster gives full mana for involved stones and double mana for mana surge (that is guaranteed on any 5 stones and more, I believe). Any skull cluster gives attack damage only with maximum +2 bonus, regardless of amount of involved skulls. There is “critical hit” that is supposed to be analogue of mana surge - but it gives nothing at all.
Most of mana attacks can hit arbitrary target - or even all units at once. Skull attack can hit the first unit only.
You can deliberately block skull attack: with magic shield, with damage reduction, with evading - simply placing unit at the upper positions. You cannot guarantee blocking of magic attack, as you cannot predict it’s attack pattern in most cases - and only submerge can shield you indefinitely (there is also hiding, but it works only while there are other, non-hiding units).
There are innate reflecting abilities that can turn enemy attack against him - again, for their use it’s enough to put the unit at the upper position. There are no magic reflecting innate abilities, and existing effects reflect damage only once.
There are tons of units with magic attack that totally ignores shield. But only handful of units that can sometimes ignore shield with a skull attack.
And for all of that, skull has only one redeeming trait: you can hit the same target repeatedly or simultaneously with several attacks - if you are very lucky. (Note that there are several magic units that can hit the same target several times too).
I think, it’s the very wrong situation and must be revised to the side of more skull damage. Actually, even simply making it on level with magic damage will improve them immensively.
And “Critical hit” looks like a bug for me. I will file the bug report for that.