It can be a really quick deck if you get a scorp out the first turn
In fact, I play my scorpion second turn (malignant is right here) only if I have nothing better to play (specially if you have few quanta). One more rewind at the end to the reach the lethal amount of poison is not a big deal. However, you can only do that if you survive the critical first few turns. I'd say put up your defence first, then hit with neurotoxin (with a few exception - see guide).
Considering all the redundancy in the deck, is only one copy of BE optimal?
I started with 2 at the beginning (idem if you take a look at the original version of eSco). Then I realised BE is quite situational. It is more "optimal" IMHO to use the slot for a better card for defence (shield, hourglass, eternity). You have only 3 scorpions. The first one is used for poisoning. The second is the adaptable one : use BE for ferox or miracle, antimatter for the FG having a lot of CC, as poisoning again for Scorpio, etc...). The last one is deemed to be rewound. I don't think an earlier BE is really needed in most cases also because it requires a lot of
. At the beginning of the game you'll prefer to use it on antimatter or pandemonium (just in case 3 light dragons appear) and you will have enough quantum to destroy each turn only at the middle/end ...