Indeed.
Seriously, look.
1:01 They're completely helpless. He has them both at his mercy.
1:45 Mako somehow bends. This makes no sense. It's been shown that bending is stopped when someone is being blood bent. Tarrlok stopped Korra from bending, Katara stopped Hama from bending, Aang was helpless to Yakone, etc. Sure, characters like Zolt are still bending while being blood bent but since it was only slight blood bending it still makes sense. Here Mako just does it...because.
2:18 Mako is back to being completely helpless for no good reason.
2:56 Korra manages to bend while being blood bent. I actually think this makes sense, since Amon has been fully charged with lightning and knocked around a lot. He's not exactly in top form at the moment, later getting knocked out. But it's still inconsistent I suppose.
So either Ozai will be helpless, or Ozai will be able to do something somehow.
The way I understood it, bloodbending nullifies other forms of bending because it prevents a bender from carrying out the motions that would lead to bending effects. Of the four types, this means that air and fire have the best chance to counterattack, because both have some method of releasing their element with little to no extraneous movement. Airbenders can release wind by breathing or other...er, ways...firebenders can literally breathe fire. What that scene showed, again in my understanding, is that lightningbending's primary requisite is the two-finger "prong" shape to grasp the electric charge, which is why Mako was able to zap Amon.