Yeah I wouldnt enjoy having to switch PA's around every time I have to rebuff.
Rebuffing is a pain in itself (yeah I have played as tank/spy for too long :( ), but having to switch the PA every time? Hell no, thats definitely not something for me.
Holy Toxic Halo isnt bad btw - if you have a good aim - If you dont, Holy Toxic Beam isnt bad either ^^