I like slow spells, but I think the cripple line is extreamly important, and a lot of enc don't even bother. Well it's nice that your tank gets hit less often, but the cleric or group healer would love it if they got hit less hard when they did also. Is this it? A lvl 56 spell (out of 80 lvls) that will weaken a mob?, and the spell is equal to a shammy and enc lvl 40 spell !!!
I know we are a different class, but if we get the spell line, why not keep it going, even if it is rather low like 56bst=40enc then have 65bst=45enc or something, it is too low to land on high lvl mobs, and solo or small group can be risky if slowed mob can still hit very hard, when it does (especially if it summons).