I'm curious if any of you competition-minded shooters have ever timed your splits when shooting your suppressed pistols (in this case let's say 9mm) and rifles (AR-15)?

Like for instance, I haven't shot any competitions in over 10 years so I'm not very good, but I can empty 10 rounds in the C zone from 10 yards with my Glock 19 with .15-.18 second splits.  I haven't timed it with a shot timer, but I'm thinking I could do the same probably with .25-.3 second splits using the same gun with an Obsidian.  My AR splits are similarly slowed down compared to using a 16" AR with a PWS556 muzzle device.

Is this something that can be overcome to shoot faster suppressed or is just the nature of the altered weapon dynamics?  What are your experiences?

With a pistol, it's probably the nature of the beast. The balance is off and the piston will slow down the action somewhat.

I'd imagine with a rifle, especially an SBR AR15, you could use a light weight and low back pressure suppressor along with AGB tuning to make the difference negligible.