Crusade is useful on PLD for the first few min of a fight. +30 Enmity means you only need 70 enmity in gear to cap(getting to +100 with burtgang was a bit tedious). The cast time is a bit long, about 2.5 seconds but it lasts for 6 or 7 minutes I think(I dunno I use Shabti Body), but it lasts long enough such that it should stay on for the entirety of most fights(unless its dispelled).