I have one rule concenring such problems - I eyeball the final result, and deem it balanced or overpowered compared to the party the PC is played in, and the campaign in question. I don't care much about the origin of spells, only the result. If that means banning half the PHB spells in one case, so be it.
As an example, I had to seriously alter the cleric of the last player who wanted to enter my campaign, even if it was a strict PHB construction. The combination of certain spells, feats and stats was just too overpowered, especially compared to the melee PCs of the party. (Not to mention that I had a serious problem with a rasta-headed jamaican (sic!) cleric named "Mr. J. Jackson" (no kidding), worshipper of a god named "Ja", when the campaign is set in the FR's Mulhorand/Unther region with a regional, exclusive pantheon...) I am still not sure whether the fact that I made him choose an egyptian name and god or the fact that I altered his PC's stats until he was not outdamaging the melee fighters by 50% in a melee fight anymore drove him off after two sessions, but I can't say I really miss him.)
The point of that whole history is: Don't focus on the source of a spell, look at the result, and at possible combos, and do not hesitate to ban and alter spells, feats no matter their source etc. if you deem it neccessary.