I've got a player complaining about that on a regular basis but that is just because we have played Rolemaster for about 15 years before and the most remembered campaign group consisted of two Archmages, a Tarot Mage, a Lay Healer and a couple of Semis. So, loads of magic there. And now in HARP he is playing a rogue and the other three are a Cleric, a Healer (own profession), and a ranger. So, this time a lot of magic but not that different magic.
To be honest I don't take those complaints seriously because the spells in HARP are basically the same you've got in Rolemaster with the difference that you don't learn a list but instead scale you spell. Rolemaster has the slight advantage that you can learn more spell more quickly ... that's at least what I think at the moment, haven't got proof for that.
As for ressources you only need CoM: Create you own spells! WAY better than RM where there weren't really working rules how to create a new spell. (Yes, yes, in RMCV there was spell research but come on that was NOTHING compared to the rules in CoM!)