I know this is probably an overasked question, but, is the loremaster learned spells really a random drop?
Yes they're random. We can battle her once and win the spell we hoped for or 100 times and get no spells. The spell itself is also random. We don't have more chance of a death spell by being on a death wizard etc...it can be any of her spells!
This next part may or may not be true as I have no way to verify it and it didn't happen to me directly: I've heard that when you win a spell it chooses the spell (through RNG) removing the ones you already know from the drop. This is why you can't learn the same spell twice and by it doing it this way you're waiting for a spell drop not a specific spell drop (which would be mighty long if you already know most of them). I think this is true because a couple of different people have said about a glitch where they learned a spell and the one that popped up was one they already had. When they checked their deck it was a different spell added that they hadn't had before.