2 life steal items in
and
is pretty excessive, and keeping you from a lot of better items.
BT on Vayne was mostly about surviving her weak early game with life steal - and Kingblade fills now that shoe. You're missing out on armor pen for Final Hour, IE for crits with Final Hour, PD for AS and Crits with Final Hour, Statik so your Final Hour crits shoot lightning, Tri Force for them Final Hour enhanced tumble shots to melt faces off, or synergizing damage with FInal Hour in general by going into a BT.
Also - Final Hour is Vayne's biggest steroid. It will eclipse the damage you're doing with Silver Bolts, so don't underestimate things like armor pen on Vayne. Sure you "can" kill a
,
,
, or
that went mega-tank in 37.5 hits. But 37.5 is hardly a "don't ever buy armor pen" kind of deal.
Avoiding Last Whisper is much more about assessing the threats on the enemy team. If theyre are squsihy threats that need to die instantly, big crits off Final Hour is the way to go - maybe even a T-Force proc. If it's someone like Nasus or Renekton, it's Last Whisper. Zhonya's can go either way.
Finally - the average game lasts ~33 minutes and sees 11,000 gold per player - which essentially translates into 3 major items. You should really plan on completing core items like Infinity Edge in your average game, and not saving it for that special occasion when the game's landscape actually favors late-game champions like Vayne or you for when you get super-fed.
Your items should help you get fed in the first place. I'd definitely put IE in the top 3 items.