Well you mentioned that with the wraiths attacking so quickly you are having difficulty paying attention to the combat log hence my suggestion about not using them as test subjects. If you have some whetstones, you can probably test it against endregas - they don't leap, they don't riposte, and they have way lower damage than wraiths.
As I said, I especially wanted to test the specter oil. So it was worth it to die a couple times while testing. ;)
Never played with FCR, but without specter oil you can't damage a specter?
If you're ever gonna play TW again, do yourself the favor and give FCR a try! No need to choose insane difficulty right away, as the easiest setting is already harder than vanilla hard. But it completely changes just about EVERYTHING, you'll get a whole new game out of it. New sword models, new talents, new sign - Heliotrope was originally Flash's idea. New rules like "you need specter oil, because your attack is lower than their defense, if you don't use it". There's a big fat excel sheet included with all the details. Fights are a lot faster, vitality and stamina much less (no more 500 vit and being untouchable in the end, I think 100 is max). You actually eat food and drink milk and water for the slightly increased vit and sta regen. And much more. A lot closer to the books. I really got used to the FCR playing style and since Flash was somehow involved in TW2 (dunno how exactly), I had hoped that we get at least a hard difficulty with similar combat mechanics.
Well to be fair, it only affects one skill in Alchemy tree although I must admit not having being able to get that extra +50% vs wraith (fully upgraded oil specialization) is a downer.
I think we speak of different aspects. I mean alchemy generally, even without specialisation it should make a difference. Like in FCR, where you can NOT survive without doing at least some alchemy. In TW vanilla on easy or medium, you could got through the whole game withough brewing one potion - TW2 feels like that, even on hard. Insane might be better, but I won't start an insane run before someone mods out the permadeath and adds a different punishment for dying. One that hurts, but doesn't end the game. I know there is a tool, with which you can restore dead saves, but then you get no punishment at all and that's too easy for insane. ;)