The card is perfectly balanced, even if you take Momentum-ability into consideration. Look for example Lava Golem + Quintessence. That's exactly as bad 2 card combo, and there's really just 1 card that can stop it (Thorn Shield).
I suppose your right about the golem/quint combo ... if you ignore phase shields, wings, fog, bone wall, dissipation shield, ice shield, dusk mantle, and procrastination.
Then I guess you could then say well you could do golem/momentum which then I would counter with fire lance, rage potion, lightning, shock wave, congeal, ice bolt, siphon life, Potentially aflatoxins, basilisk bloods, and rewinds.
So as you can see the lava golem combo is not as powerful as the momentum/dune scorp because it has a lot of different cards to counter it.
Xinef I guess after reading your argument you make some good points but IMHO opinion I still feel that the nuerotoxin ability should require an upkeep cost or something because although you made a lot of good points when it came to the chrysoar point you made you did forget one thing. Chrysoar does require quantum to continue poisoning you while the nuerotoxin just requires one successful prick. I could potentially be happier if this card at least was a little more expensive to put out.