First, get as much lightning resistant equips as you can. Voracidous doesn't have that many special attacks, the worst of which is probably the leap which he will only use on a target that is far away. If the chief ever dies he'll go into a rage mode and use a big pulse attack frequently that will likely kill/nearly kill everybody. The gimmick is this:
Phase 1: Attack Voracidous and keep the Chief alive Phase 2: After a certain point in time (or when Voracidous gets to 25%) the Chief will give his huge shield to Voracidous. Mooks will spawn. IMO it's best to just try and kite the bosses and keep yourselves and the chief alive (easier said than done, the Chief has very little health and if he EVER gets caught in one of Voracidous' attacks he'll probably die instantly, not to mention the mooks will target the chief if they can). After a while the Chief will take his shields back and basically it's Phase 1 over again. If the chief died Voracidous will go into rage mode and keep the ridiculously large shield.
To anyone who wants a way to deal with his shield ( lets be honest the boss doesn't have good amount of health and almost always gets that shield added) Have a good Zero Melee user on your team and he can null the shield out or knock it down to 25% or less depending how good he is. Best case he could kill him before the shield share happens.