I have a Savage 11 .308 with a lightweight 22" sporter barrel. It is being cut down and threaded to host an Omega. I will use the SilencerCo three-prong flash hider for the mounting device. This is strictly a hunting rifle (deer and pigs). Most shots would be 50-100 yards. I would be shocked if I was ever presented with a shot that exceeds 400 yards. I told the smith to cut the barrel to 19". I'm wondering whether should go shorter for ease of handling with the can. On the other hand, .308 is not exactly flat shooting to begin with, and I do have some concern about losing velocity. 19" was chosen by looking at velocity data. What are your thoughts?

If you aren't shooting over 400, go 16"

My first thought is: The lightweight Savage Sporter barrels cannot normally be cut to those lengths and threaded 5/8-24 with a sufficient shoulder on the thread.
But, maybe your barrel is heavier.  It can also be done rather nicely by correctly adding a separate shoulder piece to a longer threaded portion, if needed.
But, you asked about barrel length.
16"plus the finned Omega with FH mount is already a 22-1/2" total barrel.
No need to be longer for what you're doing.
Unless your hogs are wearing body armor, even a 16" is going to expend energy on the exit side landscape.

If you haven't tried it already, you will be very pleased with how quiet that combo is.
I recently was present for a side by side test of two .308 700 AACs, one with the finned Omega, one with the Thunderbeast Ultra 9.
Three experienced shooters standing 20 feet behind, and also when being handed the guns and firing with their eyes closed (it was done carefully and safely)
could barely tell any difference, did not even agree on which sounded best, and all said they'd be completely happy with either.
Considering that the TB had 50% more internal length than the Omega, I was very impressed with how the Omega held up.

I went 16.5". The barrel had to be cut to 1/2 thread due to its light profile. I'm using a very light 1/2 to 5/8 adapter, which should work nicely for direct threading with the supplied 5/8 fitting.