Comment # 50 on bug 935993 from Neil Brown

The contents of modules-load.d is not particularly relevant here.

More relevant is the content of 
  /lib/modules/4.3.rc4-2*-default/kernel/drivers/md/

This should have md-mod.ko and raid0.ko. If it doesn't (which I suspect to be
the case), then that is the problem.
You can easily test by running e.g.
 lsinitrd =boot/initrd-4.3.rc4-2*-default | grep raid0

.... Ah, I think I might know what is going wrong.

You are booted with your all-yes-config kernel when you install the openSUSE
kernel, aren't you?

dracut (which builds the initrd) has some slightly complicated logic to decide
whether to actually include a module in the initrd or not.

The 'mdraid' dracut module asks the 'instmods' function (in /usr/lib/dracut
somewhere) to install all modules in drivers/md/.
instmods tries to be clever.  For example if each module is currently loaded in
the running kernel, it will be added to the initrd.  If it could be loaded, but
currently isn't, then it is not added to the initrd.

Then there is some fairly complicated logic that only applies to modules with
aliases (and raid0.ko does have aliases).  I'm not 100% sure, but I think this
logic is making unfounded assumptions (it is the checks in host_modalias[] in
modules_is_host_only() in dracut_functions.sh)

In any case, we can bypass all this logic by passing the "-A" flag to mkinitrd.
 This suppresses the 'hostonly' checks.... or at least that it what the
documentation says.  It seems that it lies.  But we can call dracut directly

So: as one final test, can you please run
  dracut -N --force /boot/initrd-$VERSION $VERSION

where $VERSION is your kernel version, presumably 4.3.0-rc4-2.gefc53bd-default

and then try to boot the openSUSE kernel.  If you don't want to that is fine. 
I've managed to duplicate the bug now so I'm sure I can get it fixed.  But
having confirmation from you that this fixes your problem would be nice.