The legendary one is the better choice than the one you currently using as it reduce Aegis cd which seems as your main skill. The cons of using that weapon is the skill it provide are low (2 ave shield, 3 aspect), and it’s a retaliation item which is not the focus of your build.
The current MI weapon you’re using is underleveled as it’s a lvl 70 item, and you’re already reach 86, there is a new base with 82-84 lvl spawn from that monster now, if you like your weapon better go and farm it. Now about the item itself, the only worth noting stats in there is the +2 vulnerability and it -8 acid resist, the rest of the skill bonus are unusable, if you feel like you need more -acid resist better go with it, if not the legendary above may increase your dps slightly.
Either way my conclusion is both item are equal but only as placeholder until you found better item.
One last question, how does dreeg venomweaver compare to those 2 weapons? Is it better or worse? For some reason it shows that I would get close to 2000 more dps with that while the legendary shows 1200 more.
The reason is because it weapon base is a scepter/dagger which deal all acid damage, instead of physical or half physical-acid like from sword/axe/mace, scepter/dagger base also have higher percentage damage compared the 3 other 1h melee weapon. That epic scepter also provide bonus for RF and Blood of Dreeg which means more flat acid damage as well as more attack speed so if RF is your main damaging skill, that weapon is the best option available since it’s coming from faction vendor.