no, its insanely good.
with it being a unique grade and a growth item, the Domain anda Enahncement effects will grow alongside it. Attack Enhancement doesn't have a given time where after killing the buff falls off, and with it adding 1% damage for every unit killed within 30 seconds, 100 enemies = 100% increase in damage, so its usefujllness will come in a seige/defence mission or just slaughter. The Domain is also ridiculous, with a 20% flat defence reduction and a 15-20 seconds fear, which would be reduced if his opponents are at a higher level, is useful in mobbing, what more if his enemies are in his level range.
@xcalibur you missed the part in the description that mentions the buff is up to 30%
also the “within 30 seconds” clause indicates that the power boost from a single kill will only exist for 30 seconds. this does not mean that chaining kills will keep it active forever, as from the way it’s worded I take it as a 1% increase for the next 30 seconds, with it having the possibility to stack up to 30% max.