The Biohazard is in a odd spot right now. Right now it is outranked by the Neutralizer as a catalyzer and the only real thing it had going for it was its shadow/poison, but now even that is shared with something else (Obsidian Carbine). Everything the Bio is is getting beat by better things. AOE poison can come from many sources (Virulent quills, Vials, Haze, etc), the blast damage is beat by Neutralizer, and even as a shadow weapon there are better choices (Umbra and Carbine).
I love the biohazard class as it is something unique but everything that is unique about it happens to be shared by other weapons. At this time I do not feel like there is a real point in picking Biohazard, and this makes me sad since it could be such a amazing weapon.
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MY catchphrase
I agree,biohazard is great,but other weapons make it seem useless.