As I already wrote, the lower the initiative, the more dangerous the threat that a unit can realize in its turn (because the more time the opponent usually has to react to it, but teleport changes everything). In this mod, the balance works exactly like that. Low-initiative units are not pushovers.
Added 2 minutes later
Sudden attack is such a dangerous feature, given the damage that some units can inflict, that it's no wonder I moved it to the Light faction; you can't just give demons easy access to such an ability. These aren't elves; they don't joke around; they kill quickly. Teleport is, in principle, an extremely powerful spell in WGE, precisely because very high damage is usually countered by the fact that it's not so easy to deliver it to the target... But with teleport, it's easy.