I guess it also depends if you're tanking it or not. A fully tanked up build will soak up a lot of the poise drain but whether you want to risk taking damage is another matter? You'd probably be better off using a Great-shield and some medium poise/low weight armour. Stick him with something pointy and preferably divine and Brolaire's yer uncle.|
In all seriousness though, when he gets below about 60% health watch out for his dark magic. The Silver Pendant will help somewhat, but the worst of his attacks force you to face away to block and absorb the damage. Locking off a boss like Manus is never a happy prospect but the closer you are when he does this, the better (free swings galore).
If God said “The Holy Spirit will come upon you, and the power of the Highest will overshadow you,” to Mary - does that mean he loves bukkake?