IMO, instead of determining EV based on the last hand, it would be wiser to calculate EV based on every single play you make where the hand goes to showdown.
Ie, if you bet t100 on the flop and at showdown you find you were 75% ahead, your EV ought to be +t75. If the turn completes villain's flush and you're drawing dead, but you bet t200, you add -t200 so now you are net -t125.
(100 * 0.75) + (200 * -1.00) = -125
Making things even worse, this number could be skewed by hero's playing style; people folding too much on the river, never seeing showdown (and therefore having an overly strong showdown range) might see an inflated EV.
So you see that there are problems with EV.
Oh and this is the "sklansky bucks" style as calculated by the old PokerEV software. I think it might be OK for husng hyper analysis, since there is a ton of showdowns - but it is generally flawed since there are a lot of hands that won't see showdown unless villain hits whatever he was chasing.