Manifestation is overpowerd.

[Tuidjy]

Manifestation is powerful. I like it this way. It's one of the very few things
that can help an attacker against a well-entrenched, well-scripted late game army.
In my last game it was used against me quite a bit. The first time it hit, it was
pretty bad - out of SCs and combat mages, it managed to nail my cook. An enchanter
with a summer sword, a wine bag and a cauldron... he did not stand a chance, and
there were some hungry, angry giants in result.

But after that, the multiple manifestations did not do much. They hit my SCs
(no contest), freshly summoned teleistic animates (trade of gems) or air mages
(mistform + orb of lightning wins every time) Now I completely agree that
assassination spells can ruin your day when they interfere with important casters'
duties before a major battle. But that is the whole point. Working as designed.

[Tichy]

This seems like its turning into one of those "It should all be math" vs. "there should be some element of luck" debates about strategy games in general. I think the devs and the long-time players have come down pretty firmly on the "element of luck" side for dominions.