and no it was never meant to be an easy job.
( i seem to remember a modal that required time travel to get the immortal's blood as part of the ritual to weaken it so that it can be killed. and then a 2nd ritual to spread it reminding power over the planes of existence and erasing the very name of that being so that it won't get any power from devotions.
also many other "lost" powers were so because of their followers annihilation. weaken enough so it was possible to imprison or even destroy or take them over by others)
beside if you think about it since you can always "repeat' the quest. i guess story wise Lolth will