Deidara was fast enough to keep up with Oonoki
In movement speed, sure. But he wasn't shown evading any attacks while at that speed. Gaara's sand isn't as fast as the speed Onoki was flying at, yet Deidara on his clay bird was struggling to be sure he wasn't tagged by the sand attacks when the fool underestimated him. He lost an arm in that battle due to getting cocky.
The reason why. I'm not worried about Konan's Dance of Shikigami is because she has never been shown fast enough or capable of such speed in order to dodge a whole village explosion. Yes she can seperate, but it's not like she can reform her whole body from one sheet of paper., and no bro Deidara was completely covered inside of Gaara's sand, and blew himself out of it. With konan, she isn't going to able to dodge A C3 nor is she going to be able to counter the C4. If she breaths it bro she's going to die.
What has you even thinking he's gonna have the time to prep them quickly? The quickest attacks that Deidara can prepare are C1s, while his bigger ones (the C3 and C4) take longer to put together. The reason I'm bringing up Konan's Dance of the Shikigami is because it would allow her to evade his C1s easily and get in on Deidara quickly before the guy even has time to prepare them. As I keep trying to tell you, he's not gonna have time to prepare those attacks because Konan will close in on the kill before he has a chance to unleash his bigger attacks.
I know she has paper jutsu, but hell even when she reforms Deidara is the type of person to a few of those clay ants on a sheets of paper, and when and if they return to konan. She's going to get blown to bits.
She's not stupid. Both are in Akatsuki, so both would obviously have some sort of knowledge on one another. Only differences being that Konan's style of fighting with her paper jutsu are more versatile than Deidara's are and she doesn't get hot-headed about her abilities like Deidara usually does. Just because he has more destructive attacks doesn't necessarily mean it assures him victory considering what has to be done to prepare them.