He deserves an A+, Lora was undefeated yet untested and Estrada showed him what it's like to fight in the big leagues. I've seen Estrada fight many times and that was by far his best performance- he didn't lose a single round and he did everything that you could ask a fighter to do in that fight: he defended well, he counter punched, he jabbed well and he landed some great power punches.
Estrada has always fallen just short of being an elite fighter but I think the performance over Lora proves that he's definitely a worthy contender deserving of at least 1 more big shot (either for a title or against a top contender). If nothing else, Estrada showed that he is the welterweight division's chief gatekeeper and he will certainly separate the worthy contenders from the pretenders and I think he proved that Lora is not a legitimate contender.
With all of that being said, Estrada looked great because Lora was simply not a good fighter and he was the type of fighter that was there to be hit all night long, which in turn, made Estrada look great. But that's not Estrada's fault- all Estrada did was do what he was supposed to do by shelling out a beating to a fighter that was there to take one and you can't fault him just because his opponent didn't perform well.
Given the opponent and his record, Estrada gave a near-perfect performance that was well-deserving of an A grade and I think that he proved that he's more than worthy of getting at least 1 more big fight against a top opponent.