@GtotheWaveAlso, the isolated dragon died in 1 round to the dwarf army. Poor Guy. I think we need more testing. yeah, solos will be tricky to balance
— Mike Mearls (@mikemearls) March 4, 2015
Sage Advice: you can download Mass Combat Rules for Dungeons&Dragons here
http://dnd.wizards.com/articles/features/unearthed-arcana-when-armies-clash