I am currently using Dell servers and I think I will be going with DSDP to help with the iDrac configs, etc.
Do I need to create a DHCP scope on my domain controller for OSD, or is that not necessary in my circumstance?
DHCP can be a very handy thing to have...
You don't have to run DHCP on your DC, but if the DC is the only other machine you have available in that network, and you don't want to setup forwarding/referrals, you could setup a desktop/laptop with a very lightweight DHCP service running on it.
Or, using boot media, you could do it manually by hand, and then do something like this:
http://blog-en.netvnext.com/2012/11/automating-windows-deployment-with-no.html
I've no personal experience with Dell servers (well not for a very long time), but there will be guides around the web, maybe even on the Dell site, to help.