Did you think it might be a good idea to strip 8 spells from Clerics and then give one back, or 17 from druids and give only 3 ? EDIT: Yeah, you are not actually removing most of those spells from them as they didn't actually have them in the first place. Where's the real list ?
They already have a very strict selection in the first place and this can make it worse. Now were they to be compensated on an equal grounds, it would be understandable, like for example kit restricted spells, or some other way. But ... the concern is playability. Play the BG2 normal campaign with a druid as your only healer and you run into very much trouble even in the primary guests as you have no way to protect against the vampires ! Unless you intent to go completely without ever being hit, by the level drain effect.
I made these changes because this is how things are in P&P. As I hope you know, the purpose of FotD is to bring everything closer to the AD&D 2E game. Due to the limits of the game, and the fact that it is realtime instead of turnbased, certain exceptions are made, but this is still the overall goal.
Which of these spells do you think they did have access to in the first place? The above list is based on a comparison of an unmodded BG:EE installation and FotD.
As for your druid-only and level drain concern, this might apply to BG2, but FotD is not compatible with that game. It only works on BG:EE, Tutu and BGT, and there are no creatures or spells here that can drain levels.
It may look like both classes lose a lot of spells, but FotD also adds a number of new priest spells to the game. And there are more to come.
The reason why the above mentioned spells do not have a sphere is that they could be what's called universal sphere.
There is in fact already a 'universal' sphere; it is called All. It contains Bless/Curse, Chant, Remove Curse/Bestow Curse, Dispel Magic and True Seeing. None of those four BioWare spells seem to fit in with these spells, in my opinion.
The Repulse undead has nothing to do with Necromancy but everything to do with being a priest.
I am open for suggestions if you believe it should belong to a different sphere, but regardless of where it ends up, this is obviously not a druid spell. Druids deal with animals and creatures of the forests. Animating and turning undead, for example, are the domains of clerics.
The concept of a sphere system is the worst thing ever... in a story driven computer game, yes it works on a PnP as you can throw things aside and remake the rules as you see fit, but not in this game.
Spheres are the divine equivalent of the arcane schools of magic, which define the spells that are available to the specialist wizards. If you believe it sucks, that is fine. This may suggest that you are not exactly the target audience for a mod like this.
And a sphere system is already in the Divine Remix mod. So you could just encourage people to use that instead.
'Hey, don't use my mod, use this other one instead which is much better'. Really? I am not saying DR is bad - I would not know since I have not tried it, but I would rather spend my time finishing this, and I am not going to leave it half done just because another mod overlaps with it.
Also the removal and adding spells has bad side effects for compatibility. And depending how exactly you do it, with kit mods or spell mods and no one can say which is the default, as it's all over the place todays.
This may prove to be an issue, but it does not really concern me.