I do think that backing up hosts configurations is enough. For my first upgrades, I used to back up my hosts configurations and ... well, vUM is just the right tool for the right job. As we use hosts profile, this is clearly not required. In Enterprise level, as you mentionned it, it may interesting to back their configuration up before proceeding. Just in case.
Regarding your backup for VMs, vDP is a good way to proceed, mainly if your VM size are not that big. Remember that 1 vDP an store up to 2TB of deduplicated datas and is limited to 100 VMs which is higher than your configuration. You may deploy up to 10 vDP appliance per vCenter if needed.
According to the storage configuration you described, the main problem using vDP in your configuration is that your vDP appliance will store its datas in the same bunch of disks as your VMs which is obviously not the best thing to do 
. So using vDP avoids problem regarding "human fault destroying files" and will help restarting faster in this case but not "hardware faults destroying all datas" (Failed Raid5 for example). A link in the KB for vDP : http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2016565.
Ludo