Manifestation is overpowerd.

[Amhazair]

For me, the most frequent use of assessination spells is to assessinate the one or two commanders of a small raiding party. That way you can stop the nuissance in its tracks with only a small investment. Manifestation is very risky in this situation (as in: not worth the risk) due to the chance of attacking the caster if it doesn't find a suitable target. Hence, Manifestation is probably the assessination spell I use the least.

This doesn't mean that the spell is useless, far from it. It certainly has its place in those moments you want to target the opposing army with a barrage of assessinations in anticipation of a decisive clash. It might very well be that you're right and that it's the most difficult assessination spell to defend against, but I feel that this is more than balanced with the fact you can only safely use it against rather large concentrations of commanders. In conclusion I'd say this spell is siutationally strong, and as such nicely balanced.