1. BC seems doing whats intended for AD Casters, though its probably still a bit too crazy on certain bruiser champions. Overall though I think its in a fairly good place as long as people don't start stacking them again. And I'm a bit surprised that people aren't, still seems pretty viable to me.
2. BFT is still my biggest worry. It's still must-rush on anyone who wants to do AP damage, both on champs who need it to be viable (Vlad), and champs who are probably a bit too crazy even without it (Kass, Amumu), with an extra bonus of being even more necessary on champs with traps or dots (Teemo, Nid, Malz, Teemo again). Your hinted at cost/build adjustments will likely have an impact, but I think it will do little to change its must-buy status and be ineffective at curbing the more OP champs abusing it, although without testing I cannot confidently say so.
3. Having the AR/MR reduction aura gone is hardly noticeable from a player's perspective due to the proliferation of BC/BFT, but I think its a good change in the shifted landscape of Season 3. Does this mean we can get Warmog's, or some other heavy HP item, back now?
4. As much as I love me some CDR, and damn do I love CDR, I worry that an aura of it might prove a small side-bonus for most champs but a too-massive boon for those who really should have to spend the gold/runes/masteries for it.
5. Only global change I'd personally like to see that I can think of right now is halving the duration of traps on the ground. The map is just too condensed, and paths too limited, for so many traps with no max placements to exist so long.