I reported this on beta before the patch went live and no changes were done to fix this issue, I am hoping that since these changes are live on retail something will be done before the new raids come out.
Originally you could setup the raid frames with a split between odds and even:
1/3/5/7
2/4/6/8
Example:
Now you are limited to the following:
Which takes up a lot of space and does not give the same functionality.
Here is an example of the current raid frames when you try to sort by group:
They basically are on top of each other and if you “pull” out the tanks they actually deform losing group cohesion.
Adding a toggle to split the groups into odd and even and stack them would be the easiest way to handle this, and allow boarders around each group.
Also when you pull out the tanks make sure they are “CLONED” rather than actually pulled out of the groups.
So please fix this issues before raids go live.
So I am bumping this cause this is now live on retail.
We have loss the old functionality of the raid frames before we used to have frames that could be stacked odds over evens:
1/3/5/7
2/4/6/8
Example 1: (Mock up)
Example 2:(Old raid from retail)
Currently we do not have the ability to do this, the best we can do in this format is:
Please add a toggle so you can split the groups into ODD and EVEN and stack them on each other.
This would recreate the old functionality we had.
Otherwise we have this mess:
Basically you can see where the tanks being pulled out cause the groups to lose form.
Those tanks should be cloned to the side not pulled out of the group.
Also whereever you put your raid frames determines how your groups will grow, so if you put it on the left of your screen it grows from the left, if you put it in the center it grows from the center, if you put it on the right it grows from the right.
It should always grow from the upper left corner down, otherwise when we move things around in our screens we end up with different results each time.
Also I don’t understand why were you able to do the following correctly:
With the tanks being cloned on top of the groups but you could not do the the same with the other arraignment.
Please fix as soon as possible this is already live and its causing raiding issues for members of my guild.
Update 
Looks like a great addon author just fixed the problem that BLIZZARD has ignored all this time, I posted about it on beta and on live but it took one of the the addon authors to fix it.
The addon, Raid Frame Anchor will not only fix the problem of where the groups are forming from, but gives you back the old functionality of odds over even.
Addon was created by TaymaraPlays on curseforge, don’t know the in game name.
https://www.curseforge.com/wow/addons/raid-frame-anchor
Here is the image they posted that shows how to configure the raid frames using edit mode to get the odds over even build:
https://media.forgecdn.net/attachments/546/806/settings1.PNG