Heimerdinger - do his turrets basic attacks proc Deathfire Torch?

I don't think so, but the laser shots from them probably would. I suspect the distinction mirrors that of the spell vamp from Will of the Ancients, whereby basic attacks don't count as spells but the periodic laser burst does. One counts as an AA from a minion, the other as a spell from heimerdinger.

I recall the turret basic attacks not procking spell vamp in S3, and it specifically only worked on the lasers. That might have changed when they updated Will of Ancients (season 4/5 ?).

The Silver Bolts from vayne shouldn't proc DFT, since they are passive on-hit effect, but the basic attack after her tumble should since it has bonus damage from a damaging ability (active). I could be wrong about that, as I have not yet tested DFT on vayne. Set up a custom game and tell me what you find out.